only reference I knew for 'diss' was
'disrespect'.

I don't think "disrespect" is a verb. I'll have to go look it up. But the whole group of them indicates a similar attitude to the person being dissed - an attitude that says that what they are saying or doing is not worth serious consideration, or perhaps consideration at all.
And, Sparteye, I remember the original "Deep Throat" too. Did you know her FATHER watched that movie? More than once, I heard. Lowlife.