Who said he shouldn't be allowed an opinion? I think some people have decided not to use their money to support a person who holds views they consider to be objectionable; and by extension they won't support a company that employs such a person. Even though I don't know what SKR has said that has people's dander up, that's a perfectly reasonable position and one of the few recourses one has under capitalism.
If a guy says "I hate X" and I find that hatred unjustified or objectionable then perhaps I will take a stand by not buying what he is selling. Again, I have no idea what SKR said that irritated people; this next bit is just an example and has nothing to do with SKR. But suppose I found out that a local merchant was an anti-Semite. That might not bother some folks, but it would bother me big time. I would make it a point not to shop with that merchant and I'd try to get other people to do the same. That merchant would be entitled to his opinion, since it's a free country, but I am likewise free to avoid shopping with him and even doing whatever is lawful and ethical to see that his business fails. In fact, if I find anti-Semitism to be inimical to the common good then it's basically my civic duty to do so. And there's very little you can do in capitalism to advance the common good and fulfill your civic duty; responsible consumption is one of the few.
That being said, again I don't know what the anti-SKR folks are on about and if it is anything of consequence. But, speaking purely generically and in principle, it's an eminently reasonable stance to modify your consumer habits based upon your moral and ethical assessment of the merchant.