Have to agree! No room here for wishy-washy, soft-voiced encouraging words. If he is consistently testing you, then you need to be consistently firm with him. "NO, we do not throw plates/food/toys, etc". And then take it away if it happens again.
On the other hand, give him recognition when he IS behaving the way you want him to. He is not too young to understand his boundaries, and he is also not too young to understand praise when it is given. I have a little guy who is VERY rough when he plays. Not necessarily aggressive (although he can get there!) but rammy-shovey and sort of destructive. So when is playing properly, I make a fair fuss over "Good job, B! Nice and gentle with the toys, so they don't get broken! Good work cleaning up!! (He's a toy-dumper)" and so on.
Patience, consistency and redirection are your most valuable tools, I think! Good luck.