We executing dozens of Japanese for using it in WW2 because it was considered so heinous. Just because our enemies might do something doesn't justify us doing it. What next? Justifying mass murder of civilians because an enemy may do so?
Irrelevant comparison. It violates the laws of war to waterboard POW's. Terrorists are not POW's.
There is no proof that it ever gets reliable information on time that is useful and other legal methods are far more effective and efficient at gaining information.
Sorry, but factually this is completely incorrect. Waterboarding in extremely effective and has proven this on several occasions. It has given us valuable intelligence when other methods had failed miserably.