First, get a list of over a dozen things you want to say. They don’t have to be true, and many, even most, of them can be versions of each other. Then, when you are in the debate, do this:
Scientist: “If there’s one thing you should take away from this discussion, it’s…
Denialist [interrupting]: Thing one, thing two, thing three, thing four, thing five.
Scientist: “Actually, that thing four you said, that’s not really true ..
Denialist [interrupting]: Thing six, thing seven, thing eight, thing nine, thing ten.
Scientist: We can’t be sure of everything but one thing we are pretty sure of is…
Denialist [interrupting]: I’m sure of thing eleven, thing twelve, thing thirteen thing fourteen.
Moderator [scowling at denialist]: Let’s give the scientist a chance to explain thing two.
Scientist [flustered]: Thing two.. Well, what is really important is that, well, that’s not important; to know why thing two is incorrect you need to understand ….
Denialist [interrupting]: thing fifteen, thing sixteen, thing seventeen, thing eighteen, thing nineteen
Moderator: Well, that’s all the time we have, please join us next week..
Denialist [interrupting]: thing twenty, thing twenty-one, thing twenty two ….
Denialist wins debate.