I don't have a problem trusting an atheist. Whether one's personal ethical code is based upon a theistic belief system, or a personal conviction...perhaps 'humanism,' or just 'enlightened self interest,' one can generally trust the honor of those who hold to that personal code. I mean, really; if I thought that one could only trust those who claimed one's OWN specific code of ethics/morals, one couldn't trust anybody at all. Honor is honor.
(added thought) Y'know, an 'honorable atheist' is probably more to be trusted than a theist who claims to be faithful, but only has honor because s/he's afraid of the eternal consequences of not being honorable. Any honorable person bases his or her honor upon a personal conviction of right and wrong as compared to a belief system, quite apart from possible consequences; doing the 'right' thing regardless of possible consequences, and willing to accept the consequences of being 'honorable,' even if they seem to be negative.
OK, that was fuzzy, but I hope the reader can figure out what I just wrote.