Yes, Obama has disrespected our Constitution many times and continues to show no consideration for it as he tries to turn America into a socialist, government-owned and government-controlled country. This is not what the Founding Fathers meant when they had created a free country where people can choose what's best for themselves.
I'm assuming that this question is centered around Obama's Affordable Care Act (aka Obamacare). Then my answer is NO, Obama has not violated the constitution of the United States by passing that. For all regards and purposes, to force someone to pay a fee not to get something, is essentially a tax. And since nothing in the constitution has anything against taxes, it is logically constitutional.