I think Marquez was intentionally slowing Rossi from catching Lorenzo. To start with he late braked to let Lorenzo through and then slowed down to keep Rossi behind. Lets not forget that in all the laps leading to this crash, Marquez was very aggressive in overtaking Rossi to the point that it looked like he wanted Rossi to crash out.
Also, while it looked like Rossi kicked Marquez, that was not the case. Rossi ran wide to slow down Marquez who then leaned on Rossi and touched him first leading to Rossi's leg slipping out. In fact, in that footage it was clear that Rossi was driving very slowly along side Marquez, which shows that Marquez was indeed driving slowly to block Rossi.
I would hand Rossi a 30 secs time penalty instead of stripping him of all his points in this race.