I don't get the outrage? Why did he vote against it?
I lived in AZ during the whole MLK controversy. It was ugly.
1986 our then governor Bruce Babbit (who is a very nice guy as is his wife, Hattie) declared the holiday a state (paid) holiday by executive order. He did that because he (with good reason) didn't think our conservative state legislature would approve it.
In 1988, Ev Mecham, a local car dealership owner and the kind of guy who ran for office every year, was elected because (uh oh) the Dems had a party split and one of our candidates ran as an independent, split the votes and Mecham won - without a majority.
Well old Ev promptly rescinded the holiday, making such comments as "I guess King did a lot for the colored people but he doesn't deserve a holiday" and "You folks don't need another holiday, you need jobs." (The latter declaration made to a group of black community leaders.)
Evan Mecham had other problems though - he holds the distinction of being the first governor to face removal from office through impeachment, recall and felony indictment - all at the same time!
Well now AZ has no King holiday and our governor is a nutbar with a ethics problem - not a good image for the state.
Mecham didn't even last a year as governor, and his successor tried to get some version of the holiday back on the books. They did that by swapping King day for Columbus Day, which set of a new round of protests from Italian Americans. Enough outcry over that put the holiday on hold pending referendum. Then a second bill was passed, consolidating Lincoln and Washington's birthdays into one to make room for King day. That was also put on hold pending referendum after much public outcry.
So then we had an election with two versions of the holiday on the ballot. And again, votes were split, neither had enough votes to pass, and now AZ really looks like a state full of bigots who voted against MLK Day (although the overwhelming majority of voters did support one version or the other - wanting an MLK Day.)
The NFL took away the Super Bowl - which Tempe was supposed to host - and a travel & tourism boycott was imposed.
Finally in 1992 then-governor Fife Symington (who has another spurious connection to McCain) introduced a single, understandable, referendum on King Day that passed, ending our long state nightmare.
McCain voted against the holiday in 1983. He was on record as opposing Babbit's declaration of the holiday in 1988 and had not changed that position as late as 2000 - even after seeing the national beating AZ received over the controversy.
I don't know why he opposed it, but I can certainly understand why, given Mecham's comments, opposing the holiday became associated with racism. It was in AZ's best interest to pass the holiday.