You qualified '->-bleeped-<-' with the world 'freak' which most people would take as being derogatory, even without the word '->-bleeped-<-' in the sentence.Well, I was being a bit cheeky.

But if they are talking about trans people in a derogatory manner, then it's offensive, regardless of their word choice. Because that's what "derogatory" means.
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If your friends are offended by the standard abbreviation for "transmission," then it's offensive, sort of by definition. But I'd say they're being overly sensitive.
As for your coworkers, if you are not offended, then there's no problem. Except that if you think they're using it in a "negative sense" and attacking you, that's kind of a problem. I mean, isn't that offensive on it's face? If they are just using "->-bleeped-<-" to refer to a trans person, but aren't being negative otherwise, you might want to tip them off that a lot of people see that as just about as offensive as the "n-word." I see it that way, myself.