1. Often "you can't handle the truth" is used for something that is... less than the truth. The speaker wants it to just be the truth, with no argument, but they're ignoring some very relevant issues/context/details/data. When that's pointed out, they say "you can't handle the truth". No,
you (the one claiming this is "the truth") can't handle the complexity of reality, and are using this cliche to try to stop conversation that is threatening to make you deal with all the complexity of the real world. We're not actually upset (maybe a little annoyed at this person who won't listen accusing
us of being unable to handle the truth). It's more you who are upset, and are either projecting that on us or pretending that it's us.
2. If you tell me the truth and you're a jerk about it, I may get offended by the truth, but I'm almost certain to get offended by you being a jerk. You are absolutely the cause of that part of us getting upset.