The truth here is that old people suck. I hate them. The OP probably wasn't doing anything wrong. Old men especially think that they can do whatever they want. If you met some of the old A-holes I work with you'd know better. I was in a bank line one time an this old prick farted so loud and did not say excuse me or anything. There were some young girls behind him. I mean come on.

I've never met a single person who says "excuse me" after farting

I don't ever say "excuse me". That has to do with the fact that I normally don't fart in front of people... Except for my ex girlfriend. When I fart in front of her, I actually try to make sure my butt is in contact with some part of her body, preferably her face. Oddly enough, she begs me to go back out with her. She has weird taste.

170- How many old peeps do you hang out with? In public you should say excuse me. It's called being polite. Google it.

...Being polite usually means not being rude. You have a thing or two to learn about politeness.

The only polite thing to do after conspicuously farting in public is to offer whoever is in hearing range a high-five. I'm sure Emily Post would agree with me on this one >.< In other news, my grandmother farts like a cartoon car. Every step she takes is followed by a polite little "Putt" and an "Oh!" How she can still be surprised every time is beyond my comprehension.