I believe it is simply unethical--but the temptation to "sell" one's POV when an audience is captive is hard to resist.
If evo-teachers had disciplined themselves to talk as scientists should speak, in language heavy with qualifiers and "mights" "likelihood" "best possible explanatin" "plausible" "meets the minimum particulars"--they wouldn't be dealing with this challenge. Instead, they're playing catchup because too many of their own gave in to bullying.
Actually, I have seen some our arguments on these threads dismissed as being inadequate just because they contain too many qualifiers.