If they advocate it in a way that is not abusive (and there are certainly abuses of long-form platforms, too, mostly involving a Gish gallop and the use of too

If they advocate it in a way that is not abusive (and there are certainly abuses of long-form platforms, too, mostly involving a Gish gallop and the use of too much data to check each case of misuse), sure. I think then the "best cure is more speech" argument kicks in, and people can just rebut the argument on its merits. If you say the argument cannot be easily rebutted ... at some point the question turns into, "Ethnic nationalism is obviously wrong, but if someone made a coherent, logical, good-faith argument demonstrating that ethnic nationalism was definitely right, would you allow that argument despite it being obviously wrong?" which isn't very well-formed. :)