It just seems kind of unfair to my opponents to be able to play that many minions on their turn like that.
The combos you mention are perfectly legal, in fact, they are in some extend the core of the game - stealing bases from your oponent. Got hammered twice today by a Ninja/Robo comination with more or less exactly the same effects you mentioned....
It is Smash up, after all, in this Smash up right in your opponents (or mine, in my game)
And yet I can still understand you - it _feels_ a bit unfair (but it ain't). ....