A single panther would not stop that from happening (A couple of stugs will). Thit shows that a panther is not efficient (and therefore not effective) vs churchills. Panthers are not hard counters. Braindead players comparisons are out of this scope please. Even when 1v1, a panther will have a hard time fighting off a churchill in tight spaces, but this case is very situational, like a flanked MG, meanwhile in open map snares and support units will kill any chasing panther. Loosing both units at best.
If a frontline is well defended vs AT (2 stugs, lots of ATG) is reasonable that a single churchill wont do, but there is no reason for churchills to be infalible either. Using artillery or flanking is the solution there.
I also agree with most of this. The main thing with break through units like the Churchill, but also King Tiger and to some extend the Tiger (in general they follow the same "slow but durable" concept, with firepower scaled to the price) is: You usually can't stop them on their offense unless you can heavily outplay your opponent. The question is how well you can mitigate and evade the damage. Because if you can fall back and kite the Churchill, your Panther should be alright for further combat afterwards while the Churchill needs to go back and repair. If you mitigated enough damage from your other units, you can start to counter attack.
So to which extend should a 165 fuel (plus side-tech) unit be able to enforce a different play style from your opponent? Well, since a 150 fuel Brumbär and 185 fuel Panther can enfore a drastic change in playstyle as well.