Is the garage outlet rather on the loose side? If it's not good and tight, I would suggest replacing it (or getting it replaced) with a good quality spec grade outlet. Outlets with worn out contacts are far more prone to arcing than those with good tight contacts.
As others wrote, plugging or unplugging with the load or power switched off somehow--whether by the breaker in the motorhome, the breaker for the house outlet, or a dedicated switch for the outlet--will prevent any arcing. If you are doing this at all frequently, a circuit breaker that is acting as a switch ought to be rated for switching duty (typically labeled "SWD") as normal circuit breakers aren't designed for routine switching. If it were me, I would prefer to install a properly rated switch for the outlet over using a circuit breaker as the switch--in fact, that's exactly what I did for the RV outlet I installed at my house.