Oh boy. I sure like sacrificing my 3rd Volks squad and thus losing map control just to be able to fire a single shot 10 meters next to my enemies LV.
That's not argument, that's noob excuse.
If you need a counter to a unit, you build it, especially if you have it unlocked right from the start.
You not building AT weapon vs vehicle when you can is 100% on you.
And guess what?
If you kill that M3, you have a free capping unit, already present deterrent for him to make next light vehicle as it'll have no shock value anymore and he doesn't have his LV and fuel, giving YOU the unit advantage.
OKW is in perfect situation here, if you complain, you do it purely for the sake of complaining.