Look at the cap a different way. Much simpler to consider an example. If your transmitter is putting out 50 watts into a 50 ohm antenna load, the capacitor has to pass 1 amp of current. Pwr = I sqed times R or 1 x1 x 50 ohms. That little receive only tuning cap has to pass 1 amp of RF current. The plates are so close together and the insulation between them cannot handle the current alone without heating to destruction let alone the effects of voltage punching through the insulation between the plates. You really don't need to consider anything else about it on a practical basis. The current heats the insulation, the voltage pulls electrons out of their orbit (in the insulation) that causes the physical destruction. These parameters are not present (to such intensity) in a receive only application.