By joining the Liberal party, it doesn't entirely secure their vote. Party unity is not just a vote. If they were to, say, vote WITH another party regularly, or if it could be proven that they had other interests in mind during this vote then it would be understandable that they could be 'disciplined' for it, but that's a case of specifically breaking party file. It's not irrelevant that the democratic process would be jeopardized by their party, as this is the party that will most likely be next to lead this country. If this party leads the country under false guise of a democratic union then it would not only be a disservive to their rank and file, but also to the nation and every other nation that does business with and is under the thumb of our trade and any political vote that affects them. Not that we're the pivotal nation to hold together decency in the world, but we really SHOULD be, and it's plain to see that we have the opportunity to be. Party based voting is secondary to the rule of democracy and a vote for one's constituents.