It looks like you're a throwaway, but I'll bite. If you follow the conversation, you see that 'tptacek isn't using appeal to authority to defend an argument. Rather, he was responding to an abrupt dismissal of two people. He also clarified that he doesn't necessarily like or agree with either of them.

There's no appeal to authority here. If the parent had actually made a strong argument, Thomas might have responded with an actual argument as well.