He cussed at my Dad, what should I do :(?

[Tash]

So, a few weeks ago this guy joined drama club, called 'M'. He flirted with a bit on Facebook/text, but I didn't flirt back as I don't like him in that way. Anyway, fast forward, last night we were texting, and this was the conversation:

M: Gay marriage has been legalised!

Me: my dad's mad at that....

M: ****-hole.

Me: oi don't you dare cuss my dad.

M: it was called for.

What the hell? Then he tried to say i'm a bad person, and I haven't done ANYTHING! what should I do? We both go to drama club together, and it's only 4 days 'till I see him again.

1. Who was in the wrong?

2. I'm really upset, because 2 years ago my dad had cancer, and this year we thought it'd came back.

Please help me.