Why not both? Ted Kaczynski was an important thinker whether or not you agree with his thesis and methods. ISAIF was published in newspapers and the sky didn't fall.
I don't regard him as a philosopher but rather an agitator, not unlike Thomas Paine or (insert your preferred historical figure here). This largely because his writing is not in a spirit of inquiry over where technology might go, rather it is conclusory - industrialism is path-dependent and net negative, with the only open questions being how to undermine it effectively.
He's no different than the many, many cranks writing ill-informed manifestos online.