some people are harder to come out to.

[pellaz]

you have talked to them twice.
get together some literature if they read. may be a better method to explain who you are and what you are not.

I bet they have never met other gay people, have them attend a gay affirming catholic church with you:
divinity in Colorado

finally be the bigger person, accept them for who they are. Parents do not have any larger insight into life than you do. For example they might not be able to handle their own sexuality (internally homophobic), the only way they could raise a family with success is to have lots of structure (catholic church) in their life. You said your parents sheltered you, their parents and later the catholic church sheltered your parents.

if you are looking for emotional support and they are un willing un able to support your needs dont hold it against them if you cant create your own affirming environment either