unless its something super rare, if you want to paint it, paint it.

Everyone talks like repainting will make it lose its value, but I've yet to have a single bike collector come knocking on my door offering cash for my rusty old bike.

Will it loose finanical value? probably, but if repainting a bike makes you happy, makes you ride it more, and makes your time with it better, then go for it, and roll on by the haters who keep their vintage bikes in the garage.