Why is making fun of someone’s height accepted but making fun of someone’s weight isn’t?

To clarify - I don’t think either is okay.

The body positivity movement was all about loving everyone’s body, no matter what size or shape. Many people were huge proponents of this movement and advocated for loving all bodies. However, something I don’t understand is why is it accepted to make fun of short people, specifically men? Even worse, overweight people have a space in society to share their grievances safely about the struggles of being overweight, even though most, if not all cases, are due in large part to their own lifestyle habits. However if someone were to share their grievances about being short, it’s even weaponized ever more.