Short explanation on the "M$" thing

Not too long ago I was reading some forum or wickedly long e-mail thread (can't remember) and someone mentioned that referring to Microsoft as M$ was immature or something close to that point.

Well I disagree. I think most people that use the M$ thingy do it because they've grown so used to checking for files with DOS line endings with grep -lR -e '^M$' *
that they just associate DOS with M$... I mean Microsoft. Wait, I'm confused here.