Is he really though? I mean, superficially one might assume such a thing about a lightning-rod figure like rms, but is there any actual evidence of this? And, if there is, is there actually any way to quantify this effect and weight it against the positive effect he has?

I can't prove my case either, but I still believe that - on balance - rms is a positive influence. Note that I'm not saying I agree with him on everything... I'm no Stallman acolyte or anything. I just think esr is overstating the case for any damage done by rms.