It's something I think everyone tends to agree does happen, not just with this topic but with nearly any topic really. Different forums'll stir up controversy about some other site and people will spill out from those forums onto places like Reddit or Youtube or whatever. But somewhat maddeningly it's not exactly easy to prove or trace back. (If it were we'd probably have people calling it out a lot more). Also, it doesn't even have to be a 'conspiracy' necessarily as the same basic effect can occur 'naturally' just if you consider say a thread on stormfront that might have 20 bullet points about why a certain topic is bullshit, maybe a few hundred people read that and of that few hundred a few dozen get fired up to go posting all those bullet points around elsewhere. Easy to see how that could create the impression of a coordinated campaign when it is just enthusiastic individuals sourcing from the same place and winding up on the same site.

I'd say, if you were genuinely interested in trying to figure it out, your best bet would be to keep logs of the accounts when you see them, screenshots and links, timestamps and the likes. But it'd be a lot of work and you might not find out anything and just wind up looking dumb in the process. Alternatively, if you suspected a specific site like SF or 4chan or whatever, digging around on that site might yield a thread where people are talking about going out and spreading a message or whatever, but again, it's probably too much effort for too little result when there are other explanations that 'fit' too.

It is frustrating though, because even in totally innocuous subjects like video games or gadgets or sports there are accusations and vague bits of evidence of this type of astro-turfing going on but as far as I know there really isn't any good way of catching it which makes it sound paranoid or conspiratorial which just makes things worse.