That pull request has already been merged into Bitcoin Core. It will be part of the 0.15.0 release. This means that if you run Bitcoin Core 0.15.0, you will be disconnecting all segwit2x nodes.
Is this the commit?
https://github.com/bitcoin/bitcoin/commit/1de73f4e19fe789abb636afdb48a165a6fd31009Bit odd no mention of SEGWIT2X in the commit comment. Also trivial for BitcoinCash to just stop publishing those bits and then will stay connected...
Or run a fronting BitcoinCore node with this commit removed.
And I am still confused why everyone is so scared of HardForks. If the developers, user-base and miners are all in agreement they just happen. Only issue with this one is the split in opinions. But if the developers started backing it (say supporting in 0.15) then the userbase would follow I expect and the whole issue would be solved.
Feels like the main objection is from the developers is saying it is risky - but is only risky because they are not supporting it!