How would you react?

Okay so my older half sister (I'm 21 she's 23) just recently started seeing this guy a few weeks ago. He's super disrespectful & arrogant, for example: When he was asked to keep his voice down because everyone was sleeping at her moms house, he said "how much is this house worth? I'll pull my checkbook out & buy it so I can be as loud as I please". He says things like that then plays victim when we tell my sister we don't like him & that we don't want to be around him.