@Midwesterner and @sam: Ok, I change my opinion a little. See below.
In a nutshell, many places chazal says that do something for the wrong reason, it will eventually turn into the right reason, or as long as you keep connection to torah, there is hope, but they also clearly did not want reshaim learning and poisoning the well.
The baalei haTosfos tried to synthesize all these ideas with various quotes (including the one you cite) which are summarized by an article I found and quoted below
Article is written by Dr. Benzion Sorotzkin, Psyd. discussing educational rewards and cites to many of the different places that the concept of lshmo vs lo lshmo are discussed.
So despite my initial doubt that tosfos could be relevant to trolling on an anonymous internet board, (and I still note that someone who trolls an internet board could still learn lshmo), I suppose I can see the argument that no one should learn who is doing it to mess with others (tosfot) and I agree that if someone is learning to be able to troll on an internet board, I suppose that might fall within the citations.