Do you understand how symbols work? An outfit can most definitely be considered offensive.
Why, yes, I do understand how symbols work. In fact the letters we're using to communicate now are symbols. As are numbers. Do you think any letters or numbers are offensive? I'm going to conclude "no" on the assumption that I'm communicating with a rational person.
Symbols themselves are not offensive. It's how a symbol is used or how others are lead to perceive it that makes something offensive. In this case it does not appear that the outfit was being used in an offensive manner and thus not leading anyone to perceive it as offensive.
Anyone taking offense at the outfit are doing so of their own volition.