I've been in Internet forums since the Internet was DARPAnet and you needed permission from the DoD to connect to it. In all that time, one thing has never changed:
When your detractors on a thread post personal attacks to the exclusion of responding to your arguments,
When they admit to being afraid that other people will read your posts and believe what you posted, and
When they keep posting about you -- not your arguments, but you -- days after your last post,

That when you know you've won the argument.
Not really a surprise: winning rational arguments happens to be my profession these day, and my bosses and clients all say I'm good at it.