I agree that one should not use language likely to offend others on the grounds of sex, sexuality, gender identification, race, religion, physical appearance etc.
I don't really like the tone of this article though - why must I know and repudiate a short and odd list of derogatory terms? And who decides what the "proper term" for a particular group is? Is each group uniform in their preference? Or is the author stereotyping people?
Whilst this article might help raise awareness, there is no substitute for being a decent person, and thinking for yourself before opening your mouth.