I've seen this "sub affects logitech stock" story a few times now, and I don't find it very credible. If you look at the 1-month or longer price of the stock, it's pretty evident that (a) a 5% intraday variation in price is totally normal and (b) the recent news that has actually hurt the stock price substantially is that their CEO resigned.
I'm skeptical that Amazon review trolls are buying enough stock to move the market.