I'm going. If possible, I'd try to find a way to let them know in a friendly fashion. One poster noted it above - "Hey, we're not stopping so we'll jump ahead. It's pretty backed up behind you, and we clear at least our group pretty quick". Smile and go. Don't wait for the 'possible' argument.
I believe I play better when I walk. The best 15 year run I had as mid single digit handicapper was when I walked. The courses I play now are too hilly and long so I pretty much ride. I much prefer walking to riding though and it just feels more like I am playing golf with walking.
Sure, maybe for you it would be -15%, but you could probably gain 5% with a properly executed JV swing - so whatever, -10% sounds fair and falls in line with the traditional vs JV swing speeds mentioned earlier with an 8mph decrease.
As someone who just likes to play and limitations are more around practice time than technique, no way could anyone convince me to deal with the time commitment of practicing the traditional swing to gain 10% on my distances. My practice time has more value spent on chipping/putting.
So yeah, I think we agree on things.