Badmouthing Others to Hide One's Flaws

Now, I am in the middle of a discussion with a group of guys throwing trash at other people's reputations and abilities. This seems add for me because these guys are the one known who are doing undesireable things in their jobs. It makes me wonder why they are doing these badmouthing of other people's abilities, are they doing this to hide their own flaws and make themselves appear noble or what they are saying is the truth. I have no monopoly of the truth but their are some evidences that doesn't give them the right to complain of other people's dirty laundry when they themselves are soiled.