I can understand if someone has a seat that he PAYS annual membership for then it’s in his rights to kick others out
I mean imagine bein hazemanim and shul is packed with brochurim and you won’t find a seat within several rows from where you daven
Should you find a seat or make him ?
But a shul should have some benches or other where anyone can sit
That being sed don’t yell at him like the antagonist in the OP