“But the motive was correct.”
As yes the old, “but we had good intentions” statement. Bullhocky, Saddam was not crazy just very ruthless and what we did was protect those that fund groups like the ISIS (hint, Saudi Arabia and Kuwait). What we did was destabilize the entire region because of a grudge match between Saddam and Bush Jr. You can try and rationalize this but the evidences speaks louder than any poor excuses you can give.
That Bush was strategically negligent in not pursuing those weapons was the sole error.
After all, absent the free flow of oil and WMD, the USA has NO INTEREST in the Gulf or elsewhere in the Middle East.
We could simply allow them to kill each other til such time as they reach Europe.