Of course it is irrelevant. Also, I called you furry looking and not furry ;-)
Not all people activate the viewing of adult content. The drive to exclude more than one tag stems from the fact that the browse features is often flooded by certain tags, mostly horror and visual novel.
But shifted to an adult gameing perspective, it becomes ridiculus, as there is quite an abundance of non-straight tags for lack of a better word. And most of them mean the same thing anyways. So if you would not be interested in that, you are out of luck. You cannot even try to search with positive tags, to avoid the content that you do not want to play, because there is no straight tag. If you want to avoid horror, you can search for puzzle, if you want to avoid vn, you can search for action or whatever, to thin out the results. But it gets better. Indicated by the testing done by xlsk you cannot even distinguish many games when looking at their short description or screenshots. Spotting furry is quite easy compared to that.
I do not know about the philosophy of itch, if they are "liberal" or whatever. But I highly doubt that the lack of multiple exclusion stems from any agenda about lgbt and to not give the ability to filter it out. The 5yo thread made it very clear to me, that this feature is not frowned upon, but hard to code. A single exclusion was coded rather quickly in that thread. Itch does not have the AAA money, and the feature, while being a QoL for some, is not essential for the platform. Just look at Steam, they do have that feature and I did not even know they have it. And I use Steam for over a decade.
I read a lot of descriptions and comments on adult games. "Queer" stuff is not a problem. In any game with enough complexity there will be some non-straight things. And if the mc is optionally or mandatory gay, that is clearly labelled, as the dev actually wants to attract players that are interested in that. What really is frowned upon is ntr. That can be like mineral oil in a drink of water for some players.