I presume they had an arrest warrant. That allows them entry if they BELIEVE the suspect is present. Believing means more than he lived there a few years ago. There should have been some background info garnered such as a mail view, phone records, utility and tax rolls, and perhaps a surveillance to put the person at that residence. Anything short of that is misfeasance and rises to the level of a constitution violation of their resident’s rights. In such situations, agents and their supervisors can be sued personally and in this case they should.
I don't know where you got that, but you couldn't be further from the truth. Law enforcement is legally protected from lawsuits arising from anything that happens in the pursuit of their duty, even if they are in err.