“Not necessarily a sinner, Boogieman, but an unexpected and not a normal way of getting the point across.”
True, an ass speaking is an an unexpected and not the normal way of the Lord getting His point across. However, an ass speaking to you is also an immediately apparent miracle, like a burning bush speaking to you. A man claiming to speak for God, is not self-evidently miraculous though, since men can and do lie about such matters. That’s why I think one needs to apply the standards laid out plainly in Scripture to test whether the message is coming from God, or from a mere man, lest you be misled.
Yes, and according to John, it is actually possible to share in the wicked work of a false teacher:
As we obey the command not to be gullible, but "test the spirits" (1 Jn. 4:1) so that we won't be deceived, we will have to carefully evaluate teachers and ministries by the Scriptures, which are always final authority (2 Tim. 3:16, 17).