No sympathy from me, buddy. Trial by fire, son. Rub some dirt in it, walk it off, and you're good to go. That's what I did back in my day.
Like I said, most of us learnt the hard way. Including me. Back when I got interested in eromanga somewhere in the middle of the last decade, you were lucky if someone checked it and gave a warning of any extreme content before uploading it. The first sites I used just gave you links for downloading plus a pic of the cover and that was it. Same with hentai anime for that matter. You almost never knew what you were getting into, though it got a lot easier once scanlation became more common and all that.
Still yeah, trial by fire and I became thick-skinned to all bit the most shocking stuff way back. But I do remember wishing from time to time that I could have had some warning somehow, so I kind of sympathise for those who miss it. ;)
Cross-dressing maybe, though that doesn't always prepare you for a trap since you might just assume that the character will start off dressed normally and be forced to cross-dress during, or at the very least that even if they are cross-dressing it will be obvious. Nothing really prepares you for the girl who is 'too cute to be a girl' until you experience it first hand. No the kind of thing you see coming unless someone has explained it to you prior.
Yaoi is very well known within the anime/manga/VN commuinity, but is still an unusual japanese term out of it. Someone new to the community who stumbles into the wrong part of it without knowing what they're getting into, might still not know what it means.
NTR is of course, a bit more obscure. Heck, that was why the HF thread was started to begin with. Just like with the first post of this thread, to give a proper explanation of what the fetish is to those who'd heard but were confused, and increase it popularity. The guy who started it notoriously went out of his way to post on every eroge uploaded to let them know "This is NTR!", not to rage but to spread the love. The only reason we're all here now is thanks to him.