I guess I'm in the minority here.
The dude shouldn't have twatted it (because he sounds like a 14 year old ned) but he should have the right to offend anyone he likes. Let's face it, most of us have called every other team and support plenty as well.
If he apologises - fine. If not, I don't really care. I wouldn't know him from Adam. But if he dishes it out, he doesn't get to complain about getting it back.
And for me that should be the end of it.
Scrambling around in the gutter pointing fingers and shouting "He said a bad word" with the likes of Humza Useless, Michael Stewart and Neil Lennon isn't really for me. I wouldn't want to be a genuine victim of actual wrongdoing and I certainly don't want to pretend to be one, especially over something so trivial.
I'm fine calling out the hypocrisy of those who hold Rangers to a different standard, for instance Graham Speirs who once lied that Rangers directors did similar but won't mention this when it actually happens, but this little cesspit of a country is still meant to have the right of free speech.
It should be fine to criticise or indeed insult without reproach another person's choices - including their rank hypocrisy, football team, political affiliation, religious leaning, and whether they want to %^*& children. As long as it doesn't go to the point where it is stirring up hatred against a group (like the SNP are wont to do) then this is hardly worth the electrons I'm spending on it.
The only things which should be legislated against are insults based on those things that a person has no control over - his/her race, gender, disabilities etc.
Everything else - if you don't like it, tell the person who offended you to "%^*& off"