Because we have a troll president, supported by other trolls, and we have even non-trolls supporting them with the same troll arguments.
Their arguments and views are those we have to deal with. I understand there is the balance of giving them credence by addressing them at all, and not allowing bad/stupid/irrational/hateful/utterly craven ideas to go unchallenged, but the former ship has sailed with them gaining political power.
Do you see any Trump defender making any arguments substantially better? The only ones I can find are those that address only the accusations against Trump that are not supported or have evidence against them, and even then those people tend to then lump all accusations against Trump in with the weak ones.