They've been running a campaign on reddit for years. They've even had a subreddit where they coordinated, though I can't recall the name. They scan every subreddit for posts about Monsanto, glyphosate, or GMOs, and attack anyone who posts negatively about them. It was always the same people.

Edit: found the subreddit, though it doesn't appear to be as active as it used to be: https://www.reddit.com/r/GMOFacts/