Sexually abusing someone that has does done nothing to wrong you, and everything to try and help you, and you did it for nothing more than a good laugh, that is not morally subjective.

Yes it is. Obviously, you see it as wrong, as do I. But someone else may not.

So you're saying there's nothing inherently wrong about -blam!- a 5 year old?

I think it's wrong, but I guarantee some people (in fact, I've seen people) think it's fine. It's disgusting to me, but still relative. One thing that I've seen fairly commonly is a child's life vs an adults. Many people think that a child's life is inherently worth more, and that when a child dies it's worse than an adult dying. However, many people value both the same. Another topic on the subjectivity of morality is general death. Many people hate seeing other people die and feel bad for them, understandably. Others however may not care. Not because he/she is a psychopath, but because he/she never met that person. They don't care about his/her life, and so that don't care about his/her death.