I really hate anal vids and one of the reasons why is that it looks like it hurts the girl because a buttcrack is small and whenever I see a dick inserted in there, I just cringe just a little bit. So depending on the responses I get, I might watch girls getting fucked in the ass a little bit more.
Well,based on the experience with my gfs,it doesn`t hurt much but it is just unpleasant for the girl(that`s what turns me on actually,not pain).
But porn guys have some huge dicks,like EE,so that is probably more painful.
The most important thing is to lubricate the ass efficiently.
Then,with a normal-sized dick,it shouldn`t be a problem.
As for you watching,I really dunno man,and I don`t care.