In my opinion, there are way too many people out there trying to force their ideas of what is or is not appropriate for someone else. There will always be those people who tell others to turn around or that their gear is not adequate. Or that they don't have enough water. That input is, for the most part, best kept to yourself. You have most likely never met this person before you meet them on the mountain. How are you to know if they are in a bad spot?
Asking a person if they need help, or like you said offering up something like e-tabs or a snack is a nice gesture for someone that is suffering, but telling them to turn around is really none of your business.
The first time I was on Whitney I had a few people do something like this to me. At the top of the switchbacks a couple of guys stopped and talked. One gave me some willow he had in his pocket to chew on like aspirin (which was nice, albeit a little odd). Later I was really struggling (and puking) with the elevation within a mile from the summit. There, several people felt the need to tell me to turn around. I think the only thing more annoying than having traveled to CA, hiked within a mile of the top, and being forced to turn around by my body, was a random person passing by every few minutes telling me about how I felt and what I should do.
This topic reminds me of a poker tournament I was in a while back. On the first hand and older gentleman pushed some chips into the middle with an extremely shaky hand. The young kid next to me said something to him about being nervous, he must have a good hand since he was shaking so much. The older man responded by saying, "no, I have Parkinsons." The younger guy appeared to want to disappear after that exchange. If you don't know anything about the person, best to extend a friendly offer of help and nothing more in my opinion.
Some of the people you deem to be under-prepared judging by their gear or pace might be the most prepared due to their fitness level or their experience on the mountain. A lot of time, the least prepared people are the ones with the massive packs, 20 gallons of water, and giant hiking boots. Consequently, these same people are also the ones that are quickest to tell you that you don't have enough crap strapped to your back and you should probably not even attempt to go a few miles.
