When big brands like Band of Outsiders came out with clipped on bow ties selling at over $130 each, pre-tied bow ties are much less seen as a faux pas. If you dig the look of a perfectly symmetric pre-tied bow tie, go for it!
There are times the situation requires a pre-tied bow tie. For example, when it's a knitted bow tie, it just has to be pre-tied in order to hold its shape well.
The only time I would frown upon the decision is if you want a pretied bow tie for the sake of convenience! Our version of self-tie bow ties are just as easy to put on!