‘Concern trolling’ is falsely pretending to agree with an idea but raising concerns, in order to sew discontent. Something like, "I agree with giving them a Voice, but I’m concerned that … ", an insincere astroturfing attempt.
‘Sealioning’ is when someone relentlessly stalks a person asking them for evidence or arguments, in order to ‘just try and have a debate’ when the other person doesn’t want to. The term comes from from this comic, which describes it well. It’s personal harassment pretending to be civil debate.