"Withdrawn" grade from an undergraduate class vital to my Master's application
A withdrawal on a course that appears key to your masters' studies is probably a big deal.  It would be one thing if your W was in something more tangential to your onward studies.  But if you have withdrawn from a class in the exact same topic that you now want to study for your masters' degree, you really do need an explanation for it.  And it may hurt your chances.

Unfortunately, you don't have a great story to tell.  It may well be true that the professor was a poor teacher, unfair, and even biased against you.  But you don't really have any way to provide evidence of that.  The admissions committee will just be going on your word.  And unfortunately for you, those are the exact sort of things that poor students tend to say as excuses.  Saying such things is likely to reflect poorly on you rather than justify your W (especially if the professor is respected in the field).  I would avoid saying these things. If you get asked about it, focus on the fact that you were taking too many credits at the time and needed to cut back.

So, what are your options?


You could always just go for it.  This might be a negative on your record, but still you may get accepted into programs anyway--especially if the rest of your track record is excellent.  It would be less worrisome if you have other classes or projects that demonstrate your ability/interest in AI.
Try to fill the gap somehow.  Either by retaking the course, or doing some other research/work in the area to prepare for grad school.