So you've never had them but are sure they're the devil's invention?
I've been in severe rainstorms, gully washers, frog stranglers, whatever you want to call them. I've never even thought about bringing in the slide toppers, to be honest I simply didn't think about them. Also windstorms that were bad enough to wonder if the 5th wheel was going to stay upright, not an issue. But these are first hand experiences, not what I've seen, not what other people have said, these are my experiences. I really liked them on the first 5th wheel we owned, enough that I ordered, and paid for, them on the new one.
And I base my statements on what I know, not what I assume after seeing and hearing from other people. I have heard from people that the Ford diesel is not a good engine, this from people who have owned them and have told me personally. However I don't tell people that the Ford diesel is a bad engine, because I don't know this from first hand experience. I may say I have heard that some don't like it.
You should be upfront with your advice and state that it is simply second-hand and apocryphal, not first hand experience, since you've never had them.