[mrob]

It's not a non-sequitur. The usual reason people believe in a god is because some religious group says that the god exists. Those religious groups usually also claim that their god is good. If they're wrong about the goodness, why shouldn't they be wrong about the existence too?

[missedthecue]

Just because someone is wrong about one thing does not mean they're wrong about everything else too. That does not follow, rationally.

[mrob]

When both things are claimed based on the same evidence it follows to judge them together.