50 Amp Rig to 15A house power.

Looking for advice on how to connect our 50A fifth wheel (2014 Alpine, love it!) to our 15A house power while loading or cleaning the camper, and conceivably for longer periods. I have a 50-to-15 adapter I got online for $35 after reading another forum here. It screws on nicely at the camper, and then with a heavy duty 15A extension cord we are seemingly good to go. I have been talking to Keystone to make sure, though, and they seem pretty skeptical of almost any solution. First helpline person, clearly not an expert, said that they don't recommend connecting to house power at ALL, and I should get an electrician to install an RV-park quality connection at home (!!). Second was more knowledgeable and admitted there are strong reasons to need power at home, but still wanted to discourage any use of house power, said it might damage the converter or refrigerator. Said we should just use battery power to put slides in and out at home, then sort of hemmed and hawed when I pointed out that their own manual says to have shore power before using the slides.
In our former fiver, 30A, we stayed hooked up to house power many times, even for long periods, with relatively few problems, and I can't believe Keystone makes a camper that you are supposed to plug in only at campgrounds. I do understand that running the A/C and microwave on 15A shore power may be a bad idea (tho we did it freely with old camper) & that you need a heavy and short extension cord and reliable breakers in the house. But with that, it should be doable, no? What solutions have people found?