It isn't a judgement, it's a subconscious psychological reaction. There's no thought process in it; see gun, like gun. Do you really think that I need to think and remind myself that I like firearms? "Oh, a firearm, hmm... oh yeah I like firearms! Neat, lemme see that book!"
As for buggery, it depends. If it's two masculine dudes, gross. If it's a masculine dude having his way with a feminine dude, nice. If it's two feminine dudes playing together, that can be pretty hot too.
I'm not into childish stuff like My Little Pony, I would glance over that cover and move on without even touching the book unless I was going to buy it for someone else for some reason.
The purpose of a cover is to attract the attention of people who would be interested in the context of the story, and from there they can read it and judge whether it's good or not. I once opened up a book with an armed guy on the cover (if I'm not mistaken; this was about 7 yeas ago, potentially even to the day) but in the first couple pages I noticed a few things that immediately stood out to me as being unrealistic so I stopped reading and decided it wasn't good enough for me. I judged it poorly based on the content, but the cover caught my attention so I checked it out. I didn't prejudge it as likely being good, but merely thought it might be in line with my own interests. Turns out, though it is technically in line with my interests, some of the context made it something I quickly lost interest in.
Pic related is the front cover of one of my books, the third one I wrote to be specific. I have a paperback copy here within arm's reach too. I took the photo myself years ago. This book has A LOT of firearms though granted not all the ones on the cover if I recall correctly. It's written by a gun nut for gun nuts, and indeed any gun nut who checks out that cover would likely be inclined to have a look, and as it turns out that's probably my most popular book besides my 5-novel zombie survival series, the protagonist of which uses one of the rifles there on the cover. If someone sees that cover and they don't like firearms at all, then they will likely not bother checking it out. I don't perceive that as being the same as them judging it to be bad before even looking at it, though some might, and that wouldn't be very nice. Still, their mind is their own and if they want to judge my book by its cover then they may.
Attached: Firearm Valhalla Front Cover.jpg (371x596, 188K)