Some things cause (or have the risk of causing) acute damage, with others, it's chronic.

I suppose that depends on how strongly the manufacturers market their motorcycles to less-safe use... for instance, marketing higher cc sport motorcycles for regular commuters or illegal motocross rather than taking them to a track.

Motorcycles, while less safe for the rider, are more safe for everyone else, and they pollute less, so in general I suppose the ethical situation is less obviously bad for motorcycle companies than for fast food companies.

Fast food and soft drinks are specifically engineered to be as enticing as possible, playing on biological cravings that are unhelpful since the advent of mass food production, and offer no other benefits other than satisfying those cravings. It's difficult to be a large-scale for-profit food business of any kind, and still be able to fully justify your company's actions, ethically speaking. However, fast food companies, junk food companies, [carbonated] sugar water companies, and to a moderate extent many prepackaged food brands, drag down the ethics of the whole industry. They're harming public health, it's obvious, and the only defense is a naive (ignoring marketing and network effects, and habitual irrational human tendencies) retort that capitalism, individual choice, etc should always win.

You can blame the consumers—the companies are just making what the people "want"—except that's not how capitalism has worked for most of the last century. The marketing/advertising/promotion juggernaut has a life of its own and significantly boosts demand for things that are bad for consumers, bad for the environment, or both.

Even if it were pure consumer-driven demand, should free-market capitalism be a suicide pact? Are consumers only hurting themselves with unhealthy food? They're driving up healthcare costs and disability costs, which raises everyone's health insurance costs and taxes. You can argue correctly that it's inefficiency on the part of health insurance companies, but that inefficiency isn't going away until it's cost-effective and accepted to monitor everyone's diets. For the moment, they have to assume that every person they cover is eating or drinking more junk than they should. The cost of Warren Buffett laughing off health ethics concerns and emphasizing that he drinks coke or eats burgers becomes an externality, not so different from pollution.

Furthermore, forget the products they make, and forget their marketing. Companies of this sort actively seek to subvert science, funding contrarian studies: that sugar isn't actually bad for you, that more carbs are good (not just for marathon runners, but for the average office worker too), that high-fat dairy and meat are the true causes of health problems, and many others.

And what do consumers gain? A little bit of transient happiness—at least, they think the junk food is making them happy, but more likely they're just at a local maximum and they could find healthier food that would still taste good, leading to more overall happiness taking into account the realization that the healthier food isn't killing them (as fast).

Buffett's response is an admission that he can't fully justify those companies' products and tactics, so he doesn't even try. It's sad. In one sense, someone's going to hold the stock, so why not him? Does holding stock of a company like that obligate you to campaign for better food standards that will probably harm your investment, in the short term at least? Of course not, and it's difficult to see how such a constraint could be added to securities law, but shouldn't some constraint like that be added if it were possible? This is where capitalism fails. Problems develop when you legally require companies to make money for shareholders and fail to ethically hold shareholders responsible for the consequences of a company's actions. It means consequences for a company's actions are going to lag far behind (decades, at least) scientific realization that the company is making money by externalizing costs.

I'm not that down on Buffett or BH for their investments, but this is a systemic problem highlighted by Buffett's public lack of concern for these issues. These are problems that need to be solved at a higher level (government) until low-level solutions are found (profitable food that tastes like fast food but that's also good for you). So far, government has been unable to do much because the people, who are hooked on these products due to habit and all the marketing, use the levers of democracy to prevent government from acting. I'm not optimistic that anything will change soon, but I don't see how that removes the ethical liability from those businesses.

What companies would you invest in if you're in charge of Berkshire amount of money?

I don't know. So the premise is: "We have to invest in companies that are ethical nightmares because there's nowhere else good to put our money."

How does that absolve you from ethical responsibility? Shareholders driven by money (as almost all are) will turn a blind eye toward harm the companies are doing as long as they can get away with it, and the courts and laws lag decades behind scientific consensus, sometimes longer when the companies themselves engage in muddying the waters about the underlying science claims made about their products or the externalities of their business.

If you want to stay out of prison, you do what Buffett does. You make light of ethical concerns because taking them seriously makes people take notice, and maybe stop drinking so much coke or eating so much fast food, and then you've indirectly hurt your stock holdings, and that would be a disservice to your shareholders.

I guess what you do, if you want to be ethical, is don't buy Coke or whatever ethically dubious company it is, and hope a group of forward-thinking philanthropic billionaires buys it instead, and that they'll move mountains to reform or pivot the company to a more ethical business model.

I don't see how ethics can mean anything at all if it's not ethically bad to hold shares in a company (BH owns what, 10% of Coke?), if you're holding it for the financial returns generated by its current business model, rather than to reform the company's unethical behavior through your stock ownership. You can say it's inevitable that someone will hold the stock and someone will get those potential dividends. However, if everyone takes a moral stand, nobody will buy the stock, the stock craters, and then someone can pick up the company for a song, then do something better like using all the r&d and marketing power for developing good food and convincing people it's trendy and tastes great, which seems to affect customer perception of taste more than actual taste.

Nobody wants to pay current market cap (or 51% of it, at least) for one of those giant unethical companies just to try to use that ownership to reform the company into something more ethical. Those companies have boxed themselves into a corner through marketing. They've convinced so many people to consume unhealthy products or products whose manufacture harms the environment, and they make such a good profit out of it, that the market cap is too high and it's too expensive for reformers to buy a majority stake and do something better.

Just because I don't see any solution doesn't mean I'm going to throw up my hands and call it ethical to hold Coca Cola stock. It seems to be all the rage to redefine words though, so if you redefine ethical to mean direct ethical implications, an investment in Coke is no longer unethical. Problem solved, I guess?

Your ethics are selective and befuddling.