I am always polite in online games with strangers, you'd be surprised how nice it can feel to get positive vibes from a player.
If I'm playing with people I know, I generally read the room and joke around, but don't take it very far. Me and my mom play Mario Party for keeps though, and the passion on display is hilarious and non-derogatory.
Trash talk can be fun but you gotta know how far is too far, and be playful when appropriate, if it's only fun with you it's probably not worth doing, and if it hurts it definitely isn't worth doing.