Mac isn't thrilled about any of this, but he does what is necessary for the protection of the realms. As long as Peter does his job Mac will honor the agreements reached.
He'll be civil and polite to all (though perhaps a hair less so to Cassius) and offer refreshments at the start of the meeting. As far as he's concerned his job is primarily to facilitate and be a witness to what went on. He'll offer suggestions when he thinks it appropriate.