Christian liberty is a wonderful thing. We have several freedoms you just would not expect from any other religion. There are no forbidden meats. We can consume alcohol. There is no specific dress code. In the context of marriage, our sex life is between us and our spouses. We are not obligated to observe any seasons or festivals, we are not commanded to abstain from such. We can get tattoos, we can determine our own fitness regime, we cannot even be compelled to give a specific amount to a specific cause, including the local church.
But with every right comes a responsibility. Through Paul, the Lord effectively tells us "just because you can does not mean you should". Self control is one of many signs of true faith. How you treat your liberty shows the whole world what it means to you. It tells us what you think about the God who set you free, your fellow brethren whom He has also set free, and those in bondage whom He seeks to set free.
It tells us what you think about God because if you take Him seriously, you will use your freedom wisely. Needless to say, we are freed from sin, not to sin, and so sin is out of the question completely. But if you constantly test the limits, staying just shy of sin, can you really be said to be faithful? Put it this way: If I knew there were tigers behind a fence, I wouldn't constantly put my fingers through it.
It tells us what you think of other believers because your actions may affect their faith. Ask yourself this: Is it fair to down a pint in front of an ex-alcoholic? Christianity does not forbid alcohol, but drunkenness is certainly a sin, and those who have escaped from it may still be pursued by it. As Christians, it is our duty to take each other's needs into account. It is far more noble to forego a liberty than to potentially plunge your brother back into his own private Hell.
It tells us what you think of unbelievers because whether you like it or not, their eyes are on you. How they see you is how they see Christ. If they see you being reckless and licentious, it doesn't matter how free you are to do such things, you may offend them to the extent of hardening their hearts.
Thus we see that while all is permissible, not all is beneficial. Your freedom is to be used wisely, and failing to do so may be a form of bondage in itself. If your freedom causes you to act like a hooligan, you might well ask if you're truly free?