Let's just assume, for argument's sake, that Mr. Blush is correct. Does this in any way diminish the legacy of Stigma?
No, of course not. God didn't personally write the Bible, but He plays a large role in the proceedings (or so we've been told). Likewise, if Stigma doesn't play live, he's still a towering figure in the Agnostic Front canon. United Blood and Victim in Pain, which together comprise the Old Testament of Agnostic Front, are both absolutely filthy with Stigma's pitbull guitar. The chopped chords, the brass-knuckles-and-bloody-teeth riffs, the feedback (sweet fancy Moses, the feedback!): Buddy, that's all Stigma. Current second guitarist Lenny Di Sclafani may be playing those riffs live, but Stigma played them first; Stigma played them best; Stigma lived them.
And as for the veracity of "is Stigma live, or is his guitar suffering from acid reflux?" debate -- prove it. Prove that he isn't playing those chords on stage. You can't. Stigma's enough of a heavyweight that he could just think about playing the riff to "Last Warning" and the atoms around him would realign themselves to make the music.