Fuck those MPs. Grow the fuck up. You get thrown an uncomfortable dilemma and instead of handling and considering it, you would, instead get mad at the person who raised the dilemma, and engage in essentially classroom bullying?
MP Dawson, you aren't betraying the Cons if you leave them. They don't care about you or your morals, and there's no trust and / or honour between yourselves. Cutting such a relationship does not constitute betrayal; what is there for you to betray?