What do you expect to gain in doing this?? They don’t need to be told this, and telling them this is bullying. Are you actually trying to hurt them emotionally?? Because telling them this is just cruel. You’re obviously a lot taller than those you’re telling this to, and telling shorter men/guys that they “won’t have a chance” with the opposite sex all over their height is just despicable
It’s not as big of an issue as it might seem. While you might hear about it online, I’ve never encountered someone who genuinely fixates on height in person.
This could be a form of avoidance. Sometimes, people might lie or exaggerate to steer clear of conflict, rejection, or negative judgment. This behavior is particularly common among those who’ve experienced trauma and become hyper-vigilant about how others perceive them. Past negative experiences might have created a narrative where you felt undesired or unloved, leading to concerns about things like height, even though that might not be the true source of the problem.
If it’s a common thing, maybe talk to a professional, but one-offs are fine. Don’t carry someone else’s baggage.
Edit:
Btw: When posting pictures or doing online dating, lots of things are missing. You can’t hear how a person is talking, laughing and directly interacting. So due to the nature of it, it’s bound to be fixiated on outer appearance. At least at first and for short interactions. I think that’s why it’s different online and in real life.