beyond my comprehension

I've been thinking lately...
about how heartless and selfish people can be
I just don't understand how people can do certain things
like...even small things..like cutting in line.. what makes you think that you're more important than everyone behind you that has been waiting in line? What makes you more special that you can just make everyone behind you wait longer just so you can get there first, even though they were in line first? I know that's a small thing, but it happens so often that it gets sooooo annoying.
And things like..the economy..and people that rob others of their money. How can you possibly have the state of mind to be so self centered that you could be like... I'm going to screw all of these people over by taking all of their money, but hey! I'll be rich and have way more money than I could ever need so it's ok!
And people that have affairs. How heartless can you be to lie to your husband or wife, tell them you've got to into work on a Saturday, but really you're out screwing another man or woman. Where will that get you? If you're not happy with the one you're with, be upfront with them, instead of keeping it from them, have an affair and then hurt them even more when they find out what you've been doing behind their back.
I just don't understand how people can do something, know that it's going to hurt so many other people, and continue to do it.