Possibly and for good reason really, if you are only fighting the dummy AI I doubt you've ever really been pushed.. Were you around in the immediate aftermath of the 2.1 improved AI with engineered weapons? Most 'PvPers' were loving the additional challenge, I think its fair to say the PvE only crowd were not and the QQ was high even for this forum.
Arguably those who PvP are more accomplished players, it stands to reason.
Well its history now but it all got quickly nerfed..
Considering we are talking about griefing and such that is the problem most PvE people have with "PvP'ers", frankly those that enjoy griefing should be even worse in your book then, because they enjoy only attacking those that clearly do not stand a chance so those people are, by their own actions, not even fighting a "dummy" AI, and not at all getting 'pushed' or challenged.
As for AI difficulty, AI can be difficult, because amongst other things it depends on your scenario, your own skill, heck you can play overly aggressive and get a lot of npc's on you if you want.
PvP players are not in any way "more accomplished", none what so ever, PvP is not special or anything or makes them better or above PvE players, so yeah, doesn't stand to reason in my book.
I mean remember when you say this, that you are also labelling people playing insane hard PvE games like Dark Soul's series and such. You can't just toss a label like that.
The entire main problem as I see it, with griefing, is that many people do not enjoy getting randomly destroyed by some random person online, no interaction, no in game gain or reason, just getting blown up because that is what that person enjoys. And that I can understand. Again I enjoy PvP and PvE myself, PvP especially when it is challenging, and to me, those that just blow up weak targets are worse then anything else, because they specifically seek no challenge. PvE'ers can seek challenge, whatever challenge the game might give, and if or if not you find that challenging is very individual, so I don't see how you or me can judge them by that?