I'd like to know the meaning of clothing as meat bags as used in the second box of this comic strips.
Just as a warm body refers to a person; just any person, valueless as anything but the most menial laborer:
See if you can get a couple of warm bodies to stand at the door and hand out programs.
A person can be viewed as meat in clothing, a bag of meat.
There is an idiom (limited) in media, Meatbag: any living thing or animal; a derogatory name for humans or other biological beings used by non-biological beings (i.e. robots, or aliens).
Red Volcano: "Worthless humans."
M'gann and Superboy: "WE'RE NOT HUMAN!"
Red Volcano: "Apologies. Perhaps the more inclusive term would be 'meatbags'." —Young Justice
In the Dilbert cartoon, you can take your pick. It may be a reference to Dilbert's boss as being inhuman or mechanical, an unfeeling entity, or just that he views his employees as worthless bags of meat.