Ignazio,

Paul's comments on hair length, for men and for women, are culturally conditioned. (They are actually based on false science of the day). We don't know that Jesus had long hair as the Bible never says, one way or another. That is just the artistic tradition (although it may have roots in the Shroud of Turin). Also, what was "long" to us in the an age of electric clippers may not have been "long" to them. 

There is no Catholic moral teaching against men having long hair, though I would stick to shoulder-length hair and presenting myself in a way that makes you clearly male (i.e., wear facial hair as well). 

Eric Ewanco

Ignazio,

Adding to what Eric has rightly said about Paul's admonition being culturally conditioned: 

Paul's concern was always the Gospel. So, when it came to these matters, he was giving instruction to Christians so that their behavior, appearance, or speech wouldn't detract or distract from the Gospel. 

In this case, he was talking about hair length and how it was perceived by others. In other instances, he talked about eating meat that might have been sacrificed to idols . . . and he would add qualifiers about things being permissible, but not always beneficial . . . and not doing anything that might cause another brother to stumble.  Here is a modern example: 

As Catholics we believe that it is permissible to drink beer in moderation. But if you're having lunch with a friend who you know is an alcoholic and is trying to stay sober, you might think twice about ordering a beer, wine, or any alcoholic beverage.  You don't want your liberty to become a reason for your friend to stumble.

So, when we come across certain instructions from Paul or anywhere else in Scripture, we need to recognize the difference between a pastoral instruction given for the sake of the Gospel and an actual moral teaching.  A good gauge for discerning the difference is whether or not violating the particular instruction, violates the Ten Commandments in any way.

That said, for 2,000 years, the Church has given us different pastoral instructions and disciplines to follow. We can't just write those off and ignore them. That would be disobedience.

For instance, for centuries Catholics weren't allowed to eat meat on Fridays. There was nothing intrinsically evil about doing so. But it was a sacrifice the Church imposed on all Catholics on Fridays. Therefore, to deliberately disobey it, was a sin.  Today, the discipline still exists as the default sacrifice Catholics can make on Friday but the Church allows us to do our own personal alternative sacrifice instead.  

Good answer, John.

This principle of non-distraction and avoiding the occasion of sin for others is violated on a regular basis today by women who don't care (or don't know) how they dress affects the involuntary arousal levels of men.