One interesting scenario to examine where taking a passive or aggressive line may both be correct is specifically having a pair and a flush draw. to figure out the most profitable approach to playing a draw. In these situations it really depends on the board texture, stack sizes, position, fold equity etc.
Just like anything in poker one size does not fit all.
Others take a more passive route and just call until they make their hand. Some guys play them incredibly fast, pounding money into the pot whenever they have at least nine outs.
It is interesting how different types of players take different lines with draws. Think about what you want to accomplish when you flop a pair and a flush draw