Am I supposed to treat older people with respect just because they are older?

To explain the situation - I’m 23, I’m sitting in a restaurant with my friend, an older man who is my friends acquaintance (60+) comes and talks with my friend without even acknowledging me, I ask him something and he brushes me off like I’m some idiot saying ‘what do you care?’.

I tell him ‘learn how to talk you fucking monkey’ and my friend attacks me asking me how I can talk to older people like that, like they’re some fucking gods.

I feel like that older people aren’t worthy of respect only because they are older. Am I wrong for saying that?