Properly designed, installed, and crashed-on frame sliders will not bend the frame. The thing to consider is the fact that frame sliders are designed to save the bodywork and frame in a specific kind of crash...a lowside. All they do is offer an alernative sliding surface for the crashing bike. In a crash where the bike does anything more than slide on its side, there is the possibility, even liklihood, that other damage will occur. That includes bending the frame. However, a properly designed slider will include a bolt that is soft enough to bend (or break) with enough side-loading so it doesn't transfer all of the crash energy to the frame.
Rarely is the question stupid, but sometimes the answer is
you need to run everything you read online through your own personal BS meter to determine if it makes sense to you.