So my response is not directed to the author but to the general public.
If I'm out running or cycling, and if someone wants to wave and smile at me, I may well wave and smile back. Or I may not. I might be dragging from a long run/ride while the smiley person is just starting out all fresh and happy. I might not see the person waving. I might be in my own world; that's why I run in the first place.
We all have an obligation to be polite to one another as we go about our business in the world. We can still do that without demanding other people's attention.
I don't mean this to sound harsh, but when I'm running, I'm out there for me. I'm not the grand marshal in a parade that was organized for anyone else's benefit. There's no marching band to herald my arrival, I don't have obligation to smile and wave at everyone I see along the route.
People who have that expectation of me are simply going to be disappointed. Don't set yourself up for that. Don't ask the person taking her first tentative run after recovering from chemo or surgery or whatever to be all smiles for you and make your day. Don't hate on her and call her a sinner for not busting out a high-five, You-Go-Girl wave.
We all run for different reasons. If you need attention when you run, please seek it in your running clubs and races. That's all about glory and showing off your achievements. I mean that sincerely and not sarcastically.
But for the rest of us just doing honest schlepping out on our own, on roads, trails, and sidewalks, please let us be, and don't judge.