When you are flying in controlled airspace, well.... there's a clue in the name. We all rely on each other sticking to the rules, and when you make a contract with the controller, and with other aircraft, you need to keep to your side of the bargain or it all breaks down.
It's really not for you to decide that you know what other aircraft are or are not in the vicinity, that's the controller's job, and she might well be working more than one frequency.
I'm sure that none of us think you need to fly into the hillside, but as GtE points out, you had plenty of time to avoid this situation, probably about four hours.
Once you find yourself needing to deviate from what you have agreed with ATC, speaking up early is vital, but nobody wins if you have an argument on the R/T.