He never took credit for "Linux," the kernel started by Linus Torvalds in
1991. His work started in 1984, **seven years** before the first line of
kernel code was written. He is justifiably annoyed that people insist on
trying to scratch those seven years out of history, leading to the
misunderstanding that Linus Torvalds wrote the entire thing, single-handedly,
from scratch in 1991. Most likely, like you, these people are driven by
personal vendettas.
He is not against "commercialization" but against proprietary "end user
licenses." Your observation that he is against gratis proprietary software
confirms this. That you can't think of a way to commercialize free software
is your problem, not Stallman's. The FSF raised funds selling it. People have
built businesses off it. This is kind of like saying that food safety laws
are anti-business, but given your tone ("ultra-liberal communist" etc) you
probably think anything that regulates businesses for individuals' (workers
and customers) benefit is communist, socialist, or whateverist.
And yes, these -isms effectively have no meaning, because ultra-conservatives
throw them around to describe anything that benefits the "common individual."
If he is "always angry"... well, being attacked and harangued by people who
absolutely benefit from your work does that to you. Over 25 years of it is
bound to have some effect.