“Never wrestle with a pig because you'll both get dirty and the pig likes it" - the source of disagreement here is about whether or not policy needs to be followed, not about the details of the policy, so stop trying to argue the policy on it's merits. You need to do a quick review of roles and authorities, clearly lay out (ideally mutually agreed upon) standards, and identify the implications of not following the policies - i.e 'if not xyz as agreed, then the PR won't be approved' or 'if sarcastic/bad attitudes in meetings, then I'll work with [the people manager] and create a PIP'.
Empathy is super effective in this situation - use the magic words 'it seems___' and get their reaction. 'It seems like you're trying to get as much code done as possible and see these policies as busy work'. 'it seems like you don't think the quality of the team's output is how you'll be measured'. Sometimes there is legitimate misunderstandings (were they told they need to write x lines this year to be promoted?), other times they're missing an implication and need a reality check.
This is great, to add to "it seems" is also the "It feels". So for OP it's something like:
It feel like you think this policy doesn't apply here. It does and we're looking for Teamwork. These policies are for the Team, skipping them disrespect everyone (not just OP)
Then PIP and boot of you have to. The bad attitude spread and bring everyone down.
Empathy is super effective in this situation - use the magic words 'it seems___' and get their reaction. 'It seems like you're trying to get as much code done as possible and see these policies as busy work'. 'it seems like you don't think the quality of the team's output is how you'll be measured'. Sometimes there is legitimate misunderstandings (were they told they need to write x lines this year to be promoted?), other times they're missing an implication and need a reality check.