This is kind of ridiculous.
What's the point of the warning system if you jump him instantly from a verbal warning straight to a ban? Small punishments first, then work your way up. You punished him for his behaviour already, so let him come back and see if he changes. If he doesn't, then you can start handing out the mutes/bans.
As well, he wasn't threatening you at all. Sure, mockery was used, but that is not sufficient enough for an IP ban.