I'm an athletic guy, and a fast hiker. I go up climbs like an escalator. If someone agrees to hike with me, there's a tacit understanding of what to expect, so if you agree to go, then don't complain when you get exactly what was advertised. I will tell you suck it up, hydrate, and eat a Clif Bar. Furthermore, I won't even agree to take you if there is reason to believe you are overestimating your fitness, and/or underestimating the trail.
Conversely, if they make it clear they want a leisurely hike, and I agree to it, then it is on me to dial down the intensity.
All that has to happen is an honest conversation about the desired intensity from the get-go, and then it's clear who's being a dick because it's whomever is going back on the agreement.
Can't we all just be mature adults about such things? I've never personally had an issue with this in almost two decades of hiking. Maybe it's because I usually avoid random group hikes with strangers?