The key fact when comes to trolling is they want to create frustration which feed their sick minds. But how can they do that, they do that by getting a feedback that is full of what they need. Let it be reaction, anger or sadness.
So just don’t replay to them. Use the platform to deal, if you think it violates their policy then report, if they have block option then block. If they have the option to delete their responses on you delete.
Because your time is too precious for you. Don’t waste it thinking abotu what to say to a internet troll that has zero value to your life. And the more you talk or argue the more stress it will put into your mind, which is completely foolish. But this is obviously not a iron-sealed rule.
Time to time if you have valid reference to debunk what they are saying just put it there. But always remember they will not stop, they will keep trying to provoke you to cause more fraustration. So just put what you want to put there, let them read and then block them.