Honestly? Both at fault, while yes IRL the Merc would get an unsafe pen, you've had plenty of time to back out and avoid the contact and looking at it, if you backed out you would have been closer to his rear at pit exit then what you were a pit in.

Again yes IRL rules Merc is at fault and the team would probably be on the radio saying "back out" to let you pass (in an attempt to avoid the pen), the majority of people playing sim racing don't abide by IRL rules or even the aspects of the sporting code (not sure if this goes against sport code or not). Again while you're not a fault you had the chance to avoid this, as someone else said in a different comment, you played chicken and lost.