I do think it is a natural phenomena of human nature to seek the pleasure and avoid the pain.

No.

Only when sacrificing a few for the betterment of many is the only viable option remaining. It is cruel to say that one group gets to live while another may not because they do not have as great a population. Because it operates under pure logic, I can accept it. I had to study it so I know a lot about this philosophy. http://www.blupete.com/Literature/Biographies/Philosophy/Bentham.htm

I don't agree that pleasure and pain (or the other similar alternatives some utilitarians promote) can ever be the be-all and end-all of moral value. I think they are only parts of the picture - useful tools for determining moral value most of the time, but just tools. For me, consciousness is the only reasonable moral good. It seems evident to me that what is good tends to lead to greater consciousness over all, and what is evil tends to lead to less consciousness. The greatest example of evil is murder - to destroy a mind and everything it ever was or could be. Lesser evils include anything that would cause harm to a being, and harm is any state that detracts from that being's conscious awareness (pain demands conscious attention and thus reduces the total conscious awareness as a whole, as awareness is disproportionately given to the pain). On the other hand, the ultimate good is to save a life, preserving a mind and preventing the tragedy of its death. Lesser goods include anything that would promote higher awareness - helping another being so that it is free to expand and grow what it truly is. Traditional utilitarians like Bentham would say that "pain" or "unhappiness" are what defines intrinsic evil, and "pleasure" or "happiness" are what defines intrinsic good. But I've always thought that this view ignores the fact that suffering's value is to alert us of a danger to or decline in our awareness, and that joy's value is only to be a rough measure of success towards the real goal of growing as individuals - as minds. Too much joy can be bad (if they invented a drug that had no side effects and was not addictive and would keep you happily high and euphoric all the time, it would be an evil because it would severely reduce the awareness of the being taking the drug). And suffering can be good, in small doses, if it helps us grow.