I viewed the longer video and saw no obscene gesture. Nathan Phillips is an agent provocateur who's appears at a number of demonstrations, many times playing the part of the aggrieved.
Besides the second act at a fraternity, here's he is at a Trump hotel in 2017.
https://www.thegatewaypundit.c...hotel-in-dc-in-2017/
And, an earlier picture at a oil pipeline