I disagree, I wouldn't ever buy anything that I think is completely ugly.
You can find boots that fit well, perform well, and look cool. To say the way something looks has 0 influence what so ever is just silly. Yeah you shouldn't buy boots that don't fit but there is nothing wrong with the look of your boot having somewhat of an influence.
You wouldn't buy the most souped up car and then put a rusting ugly ass bright pink body on it.