Clearly I don't think its offensive. If I was suspended from work for failing a drug test or for some other misdemeanor I would expect a serious slagging when I got back.
Homophobia and sexism I class with racism (I wouldn't count the washed up transsexual song as homophobia as its the washed up bit that is the point of slagging!)
Parental species? I'm not sure what you mean.
All the other stuff you mentioned fair game in my book.
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