First of all you are a nice guy, activity is good and you know the rules and its a decent app.
When you said:
I would firstly warn him with the reason of "Disrespect". Then without any request, I would explain the reason he was warned in detail, providing proof of the incident. I would then advice him in a sophisticated way not to do it again.
Maybe you can use the commands: Mute and gag?
I go with a [attachment=3647]newplussupport_2015-10-19.png[/attachment]