FBW,
Your answer makes a lot of sense and is a lot more diplomatic than Pace who seems hell bent on banning gliders from getting anywhere near cloud! One problem though, is that not all cloud on convective days have the same base. I've been at the base of one cloud, only to find I'm halfway up another nearby! As you say, to stop glider pilots from using up the 1000' vertical distance would effectively kill the sport, so they simply cannot keep to VFR rules and operate. IFR traffic boring through cloud outside CAS still risk bumping into others and not just gliders. To think otherwise is just, well ... unwise!
SS