The other day, when I was on the bus, an old lady boarded and immediately three young people offered her their seats. I was surprised by this. I asked a korean friend why they did this. He said, "In Korea, we try to think of all people as part of the family. We even call complete strangers 'Uncle' or 'Aunt." He then asked, "If it were your mother getting on the bus, what would you do?" Of course, I would also get up. But the problem is that I don't often think of other peole as being related to me.
I have been studying Korean for several years now and the more I study the language, the more I am attracted to Korean words for their different kinds of relationships. i have many friends in America, but I don't have many brothers, sisters, aunts, or uncles. In Korea, everyone can be related to me if I want them to be!
I don't know if I can say for sure that "respect" ALWAYS requires an object, but in this case, you want to use "are respected." (Or say they respect others.)
According to age conveys your meaning, but I think the sense of hierarchy is important. You might want to try in a hierarchy determined by their age.