Yes but the argument is:
Gay = Homosexual (although even that is not the original definition...)
Gay = Crap/Stupid/disapproved
Therefore,
Homosexual = Crap/Stupid/somewhat detestable.
By calling someone gay, in the context you describe, you're not saying that they are gay, but you are saying that they are displaying qualities similar to one who is gay, and the offence is in the association of homosexuals with your friends stupid actions/behaviours.
In this case, the issue in UK and Australia will be the association of the term "Spastic" with one of the evil Decepticon characters, thereby associating those who are
medically spastic with characters that are bad/evil. Although a cleverly written bio that discussed his boundless energy (as the Americans use the term) would go some way to alleviate any negative connotations, but not completely.