I am in a similar situation, but after speaking to a few people about this, I made the decision to go to the interview for various reasons. One, you should focus of making an informed decision--what if you went to said interview and were blown away by the place and program once you visited? What if there were more opportunities to publish, more fitting clinical populations to work with, or a lab that you felt more comfortable in? Second, even if you're 100% sure that you would never attend the school that you still need to interview for--assuming that you applied to programs based on fit and similar research interests, realize that this particular POI may one day be a collaborator, or a colleague, or a person you come across at a conference. Therefore it's best to at east put your best foot forward, make an appearance, and make a good impression of yourself so that SHOULD you need to work with them someday, they will have a positive memory of you.
I hope this helps!
Congratulations, and good luck!