Prove it, realistically.

And the dumbing down continues... Can you say.. 'Mandela effect '.

What the rocket is 'pushing against' is the propellant, which is why it is ejected at very high speed out through the nozzle. The thrust chamber is essentially a pressure vessel with a hole in one end. The net pressure force in the forward direction is consequently greater than that in the direction of the hole. There are many ways to describe the operation of a rocket. The force balance requires the momentum flux issuing from the nozzle to equal the motor thrust. That is simple force equilibrium. It doesn't matter a tinker's cuss whether or not the jet efflux impinges on any other matter, once it has left the nozzle it has no influence on the rocket. You can't push on a piece of string.

You mean if I sit in an office chair with wheels on it and I have a paddle I can't row across the room like in a boat ? Cheeze zoo wee, no wonder my arms are sore ?

Please tell me this is not a college course. This idiot does not know what he is talking about. The rocket motor pushes thrust out the exhaust and the force of that thrust is acting against the mass of the rocket propelling it forward through space. Atmosphere or vacuum makes no difference. FFS🖕😡