Argue that people should have the freedom to do what they like with words or whatever, but in my view, it is unnecessary to take the word gay and use it in place of crap or rubbish.  And it is tedious to deliberately swear to try to shock, or to be all hard hitting and anarchic with language (I say this in a general sense - and also as a person who lets profanities slip in plenty often in conversation with friends).

Same thing applies to 'mad' 'insane' 'nuts' 'crazy' and so on...
Here's a bit from a Scottish campaign that raises awareness of stigma and portrayal of mental health in the media etc. They are not trying to be linguistic fascists but to simply point out that it is unnecessary to reinforce negative associations wrt gender, sexuality etc when there are other phrases that can be used instead.

Media guidelines: a practical guide for Stigma Stop Watchers

Eliminating the stigma and discrimination that surrounds mental ill health is an essential part of improving the quality of life and social inclusion of people who experience mental health problems. The media often perpetuates the ignorance and fear surrounding mental health problems through embellished and incorrect reporting of mental health issues.
At worst, headlines sometimes carry derogatory language, for example `nutter', `manic' or `schizo,' which would be unthinkable in relation to race or physical disability.  The link between violence and mental illness is also exaggerated. Millions of people have mental health problems - very few are violent. This type of media reporting often has a negative affect on people with mental health problems.