As already mentioned respect has to be earned.
Maybe there are people that would respect someone for having a big dick, and possibly the change in the way they treat you could be a direct result of seeing your dick and admiring it.
However it could also be due to the way you behave. If you feel confident because you have a big dick, and knowing they have seen your dick, act more confident with them you are likely to earn their respect.
If this is the case you need to work on your confidence generally. Then you won`t have to show your dick to get someone to respect you. Which would be a good thing, because showing your dick might lead to misunderstandings in certain situations.