Most people "avoid slaughterhouses" in the same way that most people "avoid vegetable canneries". Which is to say that people don't visit these sort of facilities because most people don't have any business to do at one, nor do they think that visiting a food processing plant is a worthwhile use of their time.
Incidentally, I used to work in a bean canning plant. No random members of the public ever visited us.
The point is that people don't visit food processing plants regardless of what kind of food is being processed, not because they're scared of canned beans or seeing where meat comes from.
And certainly not because the plant is hard to get to, where did you even pull that from? The processing plant I worked at didn't even have walls, the whole building was a pavilion. Anybody could have walked in if they wanted to, but nobody ever did.
I think there's a worthwhile distinction between meat eaters and scientists.
The meat eater, even if they eat only the minimum they think is nutritionally necessary, and even if they choose meat products from sources that minimize suffering, and even if they raise, care for, and kill the animal themselves, is fundamentally satisfying only their own body.
The scientist, meanwhile, is aiming to build the understanding needed to eradicate illnesses and treat or reverse injuries, both in animals and in humans. They're even interested in building the understanding needed to replace animal meat with, e.g. vat grown meat or plant-based nutritional and culinary equivalents.
The popular image of the scientist is that they are driven chiefly by curiosity. And certainly this is true of many scientists, more in some fields than in others. But there are a lot of scientists who see wrongness in what happens in the universe, and who will push at it until the universe disgorges a way to right it. Many of them are attracted to biology and medicine specifically because that's where the suffering is most obvious.
A think a person like that deserves better than to be compared to a self-interested meat eater.
Researchers have the same incentives as the rest of the population
Researchers work for money, for prestige, ambition and a comfortable job that is white collar and ivory tower in nature.
They are detached from the suffering their work causes.
More importantly, I dont see researchers working for free or minimum wage. Most of their work is not even replicable for the sake of prestige or due to academic pressure. This implies the work is causing pain in animals for objectively their own career protection (selfish).
When we see researchers working for free, producing replicable work that actually adds to society (vs add to the bottom line for a pharma producting a marginal improvement drug) we will call their work altruistic or selfless.
Much like meat eaters who avoid slaughterhouses...