This was blown out of proportion. Feinstein did not use those words. She did however suggest that looking at post traumatic stress disorder (PTSD) and it's high occurrences in war veterans might be advisable when bringing up the discussion of assault weapons.
I believe this was around that time that Chris Kyle was killed at a gun range in Texas by a fellow service man who was suffering from mental illness. I believe she did make a mistake in bringing up this point but she did not suggest that all vets are mentally ill or should be prevented from owning fire arms.