My dog freaks out when someone picks up a small dog

My dog, a 70 lb pit husky mix, is 2 yrs old and fairly well trained. He’s submissive, loves kids and every dog he ever meets. He’s actually quite gentle with young or small dogs, but other owners get nervous and panic or react. The problem is, any time someone picks up a small dog in his presence, he goes crazy jumping and trying to get at them, but not in an aggressive manner. And of course the more the person turns and darts away, the more excited he gets. It’s like he thinks they’re playing a game of keep away, which is not a game I play with him.

How do I make him stop? Any command that works normally is ignored in the situation. I have a collar with a beep or vibration option and those don’t work here.