You accepted a clearance you couldn't fly then changed your route without first confirming this with ATC? I can see why they were a bit grumpy with you.
You should of course have done your climb performance calcs, but even having failed to do that a simple call of "climb performance limited request alternative routing to avoid rising ground " would have given them a chance to route you away from the mountain without your getting in anybody's way - which presumably was the issue.
The biggest offence against protocol was certainly changing route within controlled airspace without clearing it with ATC.
G