I think if you run on the pitch, you're fair game for a sly trip or a bit of a shoulder barge.
It's a bit like fans who spend 90 minutes taunting players and calling them everything under the sun and then getting offended if the players give a bit back
I agree with your first point. To be fair it was no big deal
The Albion fans are the worst with regards to your second point. They constantly sing about Gabby's mom being a whore, then moan when he celebrates in front of them after scoring.