Well, you can say something, but if it just turns into an argument about you not supporting him or whatever, is it really worth it? Sometimes, people just need to vent or to talk about what they are thinking. Sometimes, we need to just listen.
I have learned that lesson from my daughter. Sometimes she is not looking for advice, sometimes she just needs to vent. I used to interject what I thought were words of wisdom, but she quickly let me know that she just needs to vent to someone. I have learned to allow her to do that and keep my opinions to myself unless I am asked for them.