[JaBlue]

Stuey,
"cuz its impossible"
You're a special breed. I think for most people, though, this situation is possible. Why do you think you're different?

Reef,
"Why should anyone consider anything but their own well-being?
--
these types of people generally have no friends"

If they're happy without friends, what does it matter?
If they're not happy without friends, they're not doing a good job of figuring out what will make them happy.

pokermom,

"If my happiness is my only concern then why not kill you and your family for what I could gain?"

Well, if you are truly happier killing me and my family, then why not? For most people this isn't the case because they would be unhappy after killing someone else and they would be unhappy faced with the legal consequences involved, but maybe murderers (thieves etc.) run their own analysis like this and think they will be happy killing someone.

"If my happiness is my only concern then why not hurt and disappoint you in any given situation because, after all, I'm only concerned with myself."

Again, if this doesn't affect your happiness, why not?

"It's an excuse to put yourself before all others"
Why is this so bad? I'm contending that maybe, properly considered, I do come before all others. And that you should think that you come before all others.

I think your examples fail in this context because if I accept that I should come before all others in my own decision making it would be inconsistent to say that you shouldn't consider yourself before all others in your decision making. Though it may make me unhappy - or dead - I can still understand it.