As to the topic, yes, it is immoral. And gravely so.
That being said, people should treat it the way they treat other sins rather than as an extra-super-dee-duper mortal sin such that makes people more likely to deny and rationalize it than repent of and confess it.
Smilo, if you have kids someday, I hope you endeavor all your efforts to protect them from sin and grow in the faith. However, if you do have kids, they will undoubtedly commit mortal sins someday. They should know the gravity of their sins and yet know you and God both still love them and want them to repent and heal their relationship. One of the things I can still remember my mom telling me over and over as a small child is that no matter what I do she will always love me. She may not love all of my decisions but she will still love me. If I have kids someday I plan to tell them the same.
Well said, all of it.