"some" people?
And whether people still believe it was or not, at the time of the invasion it was overwhelmingly considered justified in the US and in many countries ... for reasons that even in hindsight were correct.
For example, Iraq was accused of violating an agreement not to research, develop, build or stockpile weapons of mass destruction and long range delivery systems ever again. The ISG found that Iraq was violating that agreement. It was continuing to research, develop and build such items. As to stockpiles, it is true that none were found, but the ISG said in their report that the possibility that Iraq moved WMD materials to Syria before the invasion could NOT be ruled out. The ISG admitted that they could not say for sure how much WMD had been produced by Iraq. The ISG said they had a "credible" source indicating a movement to Syria had occurred (and many other credible sources said they same thing). And most important of all, the ISG concluded that Saddam had not given up his ambitions of reconstituting his WMD arsenal, and that Iraq could have done so rapidly once the sanctions and oversight ended ... which was likely to have happened had we not invaded and the UN instead gave Iraq a *clean* bill of health.
Another reason for invading Iraq was to end its aid of terrorist organizations and terrorist movements. And post invasion it was found that Iraq had indeed engaged in many such activities and was on friendly terms with numerous known terrorists and terrorist organizations. It was allowing terrorists to operate freely inside it's country and even training them. Had we not invaded, that cooperation would surely have increased, and mixing terrorists with a friendly-to-terrorists, WMD armed nation, that considered itself at war with the US (and audio tapes discovered after the invasion prove that's exactly how Saddam and his top staff thought), would have been a potentially deadly mixture. Especially when those tapes prove Saddam and his top staff discussed the use of 3rd party surrogates to attack the US with WMD.
A third purpose for the invasion was to help the Iraqi people. Free them from a brutal tyranny. A tyranny that looks even more brutal now that Iraq is starting to become a model for the rest of the muslim world to hopefully follow.
As for Afghanistan, the US invasion was not revenge. It's purpose was to shut down the large training camps from which the 9/11 hijackers had come, that the Afghanistan government allowed to exist and that even cruise missile attacks had failed to close. And to end the intimate connection between Afghanistan's government and Al Qaeda. A connection that even extended to the marriage of the children of bin Laden and the Taliban's leader.
So once again, we find you are simply starting with false premises.
So you want a world without secrets. You are even more naive than I thought.