I'm no expert.....but have been around. My advice would be to NOT tell your W what your son said. She will either not believe you (that your son SAID this), or come up with a scenario in her head by which she imagined you planted this idea in his head - or are "poisoning" his mind. I speak from experience.
IMHO if something comes up with your son again, continue to be supportive and remind him that his mother loves him and will always be his mother/will always love him. Steer clear of discussion about what you think is right or wrong about W's decisions - because you don't know what (and how) will get back to W----and because your son will and should make up his own mind. Also, it is so very difficult to remember, but the relationship between your W and your son is THEIR relationship and at this point should not have anything to do with YOUR relationship (or lack thereof) with W.
If you think it would benefit your son - or if you think she NEEDS to know how he feels, suggest that he talk directly with your W-----however, in the MLC mind anything they do is RIGHT (their sense of morality is their own - and since they think it is what they want - it rules)and.......even if it comes directly from him she might jump to the conclusion that you put the idea in his head.
The kids in the middle of this are the real losers......
Me 45 M 25 yrs; T 31 yrs;bomb 8/15/06; moves out 7/18/08 D 18, D 14, S 12