The first amendment protects you from government interference. It doesn't protect people from deciding not to do business with the New York Times because they don't like what the paper says. NYT is definitely big enough to not need that extreme level of protection.
Nobody gets that kind of protection, so the size is irrelevant in each case. That's the point - the size of it only matters if tolerance depends on ineffectiveness.
There are plenty of people on this page insisting that politics should be countered only with politics, not with shunning. That can be a good policy at a small scale, don't fire people because of how they vote, etc. But it's not a good policy at a large scale, of deciding whether you work with a big corporate institution (or someone with as much money and public face as one).
One qualifier would be giving a full speech at either the democrat or republican convention. That's intentionally putting yourself into the political system, and it's okay if people make business decisions based on it.
I think it's stupid to make business decisions based on just that (of course, the content of the speech matters - e.g. if you are a coal miner and the speaker says she will bankrupt coal miners, it's prudent for you to exercise extreme caution in dealing with such person). But that's not where we are at. We are at people trying to shame YC into making business decisions they obviously don't want to make based on shaming mob's political preferences.
