I think we should be able to acknowledge the difference between "stealing" music to own and be entertained by is different than grabbing a picture on google for the sake of a post on Twitter.
People grab music/video clips from copywritten sources for Twitter/Reddit all the time. That isn't the issue being brought up by Gaga.
Because one "bad" thing is not enforced does not make another "bad" thing ok.
Try and use even a few second clip of bands music on you tube in a video you made and see how long it lasts before being taken down. There just aren't the same policing methods in place for pictures on the web. It also comes down to if the owner if the picture cares or not and what the picture is used for etc.
I just always find it hilarious when bands complain about pirated music when so often the screw over photographers by using their picture on social media or on other media with permission and without paying for it. Some of them compound their arrogance by telling the photographers that they should be happy they are getting free exposure.