“...And for Christian men, that number is 55 percent.”
“Christian”. Lots of people call themselves Christian for many different reasons.
When a Christian views porn, I'm more interested in the post-event reaction. If he or she feels remorse and repents of the sin, I'd assume that the Christian fell to the temptation of sin as all of us are prone to do at times. Our Lord is a forgiving God. He forgives even those who have repeatedly fallen if the repentance is sincere.
If a "Christian" views porn without the sense of guilt, then there is a problem. Their conscience appears to be seared and he or she should be rightfully concerned about whether or not they are truly a Christian.
A Christian can certainly sin but a Christian should not be able to sin without feeling guilt if the Holy Spirit is active in their life.
Of course, the above is not an endorsement of or a rationalization for viewing porn.