is it wrong to withold a source?

i'm not even talking about CC's in this case. some other person on another forum saw me post about opus being in stock locally and the issue i have is that i've had sources ruined just as recent as 2 months ago by people i don't personally know but ran into and told them where get some HTF's. i had a local source who use to hook me up and call me every time something came in and charge me a reasonable price. i gave this source to a few people to get a few things and it turns out one of them runs a website selling opus and other HTF's for huge amounts and now the source doesn't even call me because the other guy will pay 20$ for a single robusto opus.

so what do i do when someone asks me who i don't know? i tell them i'd rather not out of protection of my source but they get mad and tell me i have a poor attitude. yet they have hardly any posts or reputation on the forums and just expect me to trust them 100%. is that right? am i caring to much about this? i got called a f-stick recently for politely declining to tell the party where i get them from now and i've never even met or seen this guy on the forums. thoughts? doesn't the same apply to CC sources? BTW, this person is not on these forums.