Some thinking about what is happening in Libya

Recently there was very fierce battle in Libya. The United States, together with French and the UK are throwing thousands of bombs onto the land of Libya after the UN give them the right to set a no-fly zone as if the right is an order to drop bombs. However, are they really doing that out of the reasons they have given?
Yes, I also think that Gaddafi is a dictator that many Libya people do not like. Actually his administration is not legal and morally right in some sense as a dictator. Nevertheless, he has been dictating for 42 years. Then what are those western countries doing during the past 42 years? If they think they are right to do what they are doing now, why did not they do it earlier? If they think Libya people are suffering due to the cruel government of Gaddafi and those western countries themselves are obligated to give them a hand to win their freedom, why do they need to wait for 42 years?
The other thing is that while the Libya government is accused of using violence to suppress the rebellion, there is also the same case happening in Bahrain. Why are those western countries not doing anything about what is happening in Bahrain? On the other hand, if a dictator is considered not reasonable to govern a country, then why is a king? Just because he has got a name of the word “King”? Just because the kings are said to have some royal blood? This may be reasonable to accient people, but not to the people that have received modern education where democracy and equality are stressed.
Just take a few minutes to think about what happened in Iraq, when the United States launched its missiles, it claimed that Saddam, who was also a dictator, was developing weapons of mass destruction, which was a serious threat to the rest of the world as it claimed. What turned out is that they found more than a hundred thousand Iraq ordinary citizens died in the war instead of any trace of the weapon that started the war and. Saddam may not have been a kind-hearted person, but are the American soldiers treating the Iraq people better than the previous Iraq government did? Are the Iraq people’s lives getting any better because of the war?
I can find no convincing reasons to explain those contradictory facts above rather than that those western countries only do things that are to their own profits. If the Iraq and Libya do not have so much oil, will there be any war again?
It is quite likely to be right to strike Saddam down,as well as Gaddafi, but I think those western countries should have some fixed principles and criterion, rather than only do things that can benefit themselves. Otherwise it cannot be convincing enough to let me believe that they are doing those things out of a sense of justice.