The point is that whilst we can't help our *feelings*, it's a different thing when you direct that comment about people - it's not just an honest description of what you can't help, it's reasonably read as a statement that the person intentionally posted. Moreover, if it's fair for him to express his feeling, why was it trolling for the other poster to respond? He was only stating how he felt.
OK, given your position how about this? I feel uncomfortable around black people. I will qualify the statement by saying that I don't mind black people, there is just some feeling of revulsion that I get when I am around one. And according to you I can't help my feelings. Its something about the hair and some bad associations I have. But I would never think that anyone should abuse them or subject them to discrimination. I just don't want one to sit next to me on the bus or marry my sister, you know.
Now I will also tell you I am an ER physician. If you were black, would you feel safe and comfortable coming to see me in the ER as a patient? Would you feel that you would get the same care that a white person would? Would you worry that you would get substandard care because of subconcious (or concious) biases that I posess?
If you don't you'd be a Pollyanna to the extreme. (And you'd be contradicted by good research that in the US at least black people get objectively substandard care on a regular basis in medicine.)
So yes there would be a problem with me feeling that way. However I agree with you that such feelings should be expressed, but to bring them out in the open and work on changing them. Irrational fear of another group (whether its blacks, gays, muslims, or whoever) simply for membership in that group (and presumptive status as a danger or worse a predator) is wrong. And we all have it. Its part of being human. Those of us who work hard enough can mitigate its effects. However you can't accomplish that by saying such irrational beliefs are acceptable because they are feelings which can't be changed.
And in the sense of full dislclosure, I will say that when I was 20 those statements that I made were probably pretty descriptive of what I felt. (I used to have a confederate flag and a pink triangle on my pick-up.... talk about being an ignorant hick. Wait - I deserve civil rights.... but... um, they don't. Or something.) Fortunately I had the life experiences necessary for me to see those biases for what they are and to try to change them. In some sort of cosmic irony my husband is mixed race (like Obama actually, African dad, white American mom) and his parents now live with us.
Of course I'm still sexist, racist, homophobic, transphobic, ageist, classist, and all the rest. Though I've made a concerted effort to minimize those feelings in myself and more importantly to minimize the effect that they have on my interactions with others. So while I think the OP should have expressed his feelings (since that's the first step to change) your defense of leaving these biases unchallenged because they are 'feelings' is what is truly dangerous in society. He doesn't need to be attacked. But he does need to be called out on his unconcious biases. Excusing such biases as 'only feelings' is simply being an apologist for homophobia.