I don’t have a problem if someone wishes to patronize or not patronize an establishment, company or service on whatever criteria they choose.
That is their business, not mine.
I take umbrage to someone who takes a derogatory tone towards those who don’t follow the same course of action, and the person takes a “cafeteria catholic” approach to the issue. If someone wants to make an issue out of something, fine. People can accept you at your opinion.
But if one is derogatory towards others, there is an expectation of rigid consistency. It is the price of being a rigid ideologue on an issue.
Of course the same is true of Microsoft-haters, etc. It's hardly just Apple that attracts such types.
As you say, they are welcome to buy or not buy any company's products for any reason they choose. I have no issue with that at all, even if I think it's silly.
And also as you say, expecting that others will adhere to one's own rigid rules, and being derogatory when others do not, requires that one set a completely consistent example and back it up with consistent actions.
Consistency in one's purchasing choices shows that one is not merely a hater, but that instead one is using one's purchasing power in a reasoned, intelligent way.
Surely, if a bunch of vegans can do so, conservatives can do as well.