I would love grading papers! I don't think I've ever heard a professor complain about that. Why do it if you don't love it?
Have you yourself ever done it? And what kind-hearted teachers have you met?
I had TA experience back in High School, and I gotta tell ya' grading those quizzes and tests was the absolute worst part. Trying to make out the handwriting, the questionable dirt on some papers, the bizarre number of scoring systems to keep track of, the disorganized kid who turns in things really late,....yuck.
This TA time was also for just my final semester, I can imagine dealing with all this crap for years would really dampen an opinion.
And this is coming from someone who literally is going to Grad School to teach.