northguy isn't saying the nicknames themselves have a transphobic meaning, he is saying the use of any negative nicknames is people being transphobic. Or in other words, people don't like Daytona just because they are transphobic people and this is why they're using negative nicknames instead of using Daytona.
Now, if we apply that same logic to northguy, it must be that northguy only likes Daytona because Daytona is trans. Which is itself transphobic, because northguy's like for Daytona would either be out of pity or a fetish.