Did anybody here passed GCSE English? because your consensus is wrong.
Fortunately, language does not operate on a democratic basis to be decided by some greebo metal heads on a pickup website. It is pronounced loot-i-er - the Oxford English Dictionary, Collins Dictionary, Webster's Dictionary and every other dictionary says so (even the ministry of disinformation, i.e. Wikipedia).
Even online dictionaries get it right:
http://dictionary.reference.com/browse/luthierFurthermore, it does not mean gee-tar-mak-er as the word applies to makers and repairs of all types of stringed instruments (but particularly the French instrument known as the 'luth').
Those of you who have failed, be ashamed and stay over in detention until you have copied all words begining luth- out of the dictionary. :D