One should have kovod habriyos, clearly. One should show further kovod to the elderly, perhaps more so than one’s elders who might be only a year older.
The challenge could be if an elder, a kohen, or a rov (r’l) has done something that makes it hard to demonstrate respect to them.
I had this situation with someone who falls into one of the categories listed. I had a difficult challenge demonstrating kovod given certain events I knew of firsthand. I chose to avoid being around this individual rather than demonstrate a lack of kovod to him in any interaction. I certainly didn’t feel it appropriate to confront him, and I couldn’t just forget what I knew (not a matter of L’H, and not a matter of criminal nature, r’l, but of events witnessed by me and others). So I felt the best way was to stay away.
I don’t know if it was the proper thing to do, but it felt like the only choice at the time (25 years ago until his death about 10 years ago).
I never ask this on these forums, but I’d actually like to hear opinions on if I did the right thing.