If someone shows you respect, you are not obligated to have a long conversation with them. It is respectful to say 'Hi,' and to keep moving. The other person needs to respect that you do not want to have a long conversation with them.

It is not disrespectful to decline a request from someone else when you do not want or are not able to give them what they want.

You can't fix his feeling slighted, you know? That is his problem that he needs to deal with. He can't expect people to be willing to stop and talk to him just because that's what he wants.