We had the exact same problem at our Thursday game group and ended up making a simple rule that saved the whole night. Base game only for casual meetups, and if someone really wants expansions, they have to host their own table and warn people ahead of time. The turning point for us was a guy who brought five tiny card games with rulebooks longer than my grocery list and then got mad when nobody wanted to learn them at 9pm on a work night. Keeping it to one game everyone already knows means we actually finish a round and nobody storms out. Your guy flipping the board over longest road is wild, but the robber does make people act up, so I get why you want limits. You are not being dramatic, you are just protecting the vibe.