While I can laugh at Shatner’s tweet, I actually wonder if he fails to see the hole in his own attempt to discredit the pairing. If he intended to throw shade at Hook, then he’d better start by calling him Hook rather than “Killian” (something only CSers do). Neal was born the son of a peasant, as was David, and they both managed to fall in love with royalty, Emma and Snow, respectively. So to me, the reason to not pair Hook with Emma is not owing to his low status, but rather, his behavior and the attitude he chooses to adopt (selfish entitlement and disdain for the feelings of others).
But for all I know, the writers are going to ret-con Hook so that he turns out to be a lost prince of some kingdom. *twitch*
"That’s how you know you’ve really got a home. When you leave it, there’s this feeling that you can’t shake. You just miss it." Neal Cassidy