With their majorities, it is the opinion of many that the Dems ran roughshod over the minority quite a bit. I also do not care to get into a "yes they did, no they didn't" tit for tat, as we've already had enough 'because I say so" in this thread.
In the end, IMMHO, we are still a country, and a Government, of laws, and that was violated with this move. What we see in this thread, by the uninformed, is this demand to "show me the Law broken". What those folks fail to grasp is that at the highest levels of government, there are not simple statutes that govern. On issues such as Executive privilege, advise and consent, etc., what the highest levels have done is create their own in-House rules, based on the allowances provided by the Constitution, and which hope to maintain the template for functional government within contentious politics. The violation of those rules is what is known as "going nuclear", that is to blow them up.
Obama clearly went nuclear, solely to gain a short-term political advantage. I believe that you understand that he did something never done before. He has trashed the system solely for his own hopeful political gain. To those who see this as a "win", its a pyrrhic victory. Government just got more feckless and reckless.