I'm pretty sure William is an unhealthy 6w5 tbh xD Every 6 I know has a complex about what's right and wrong, and when they're unhealthy, they [i]will not[/i] budge on their beliefs. Also, he'd be a phobic 6: the kind that appeals to authority as if they're a god, and their mental stability depends on their belief that the authority knows best. If someone comes along with proof that the rules they follow are wrong, they either have a breakdown or refuse to believe the evidence because it's too difficult to comprehend.

From my book:
>Unhealthy sixes find danger around every corner. Their anxiety borders on paranoia, as they fear that the world is unfair and that most people are not who they say they are and cannot be trusted. Unable to trust themselves either, they look to authority figures and experts to make decisions on their behalf. These sixes find fault in others and tend to fall into patterns associated with the mental mechanism of projection.

I totally see this in William! He projects on everyone and takes the word of his chosen authority as gospel. He also doesn't trust anyone that doesn't follow the same rules he does xD