Yes there's always a chance some wild-eyed rightie will form a government, and proceed to try and wreck the joint, but that is a pretty small chance, and is just as likely to happen with a PR voting system.
I think a wild-eyed rightie did recently form a government. His name is Stephen Joseph Harper. Because of FPTP he was able to form a government with just 35% of the vote. Under PR he would have needed the backing of parties who represent almost half the voters to form a government.
And Stephen Harper was very much opposed to abortion on demand and medicare generally, but we still have both. Explain to me how it was that he was unable to implement the program he so clearly wanted.
He was unable to implement it because if he even tried to, the Conservative Party's level of support would have plummeted to under 25% and even under FPTP that low level of support would have marginalized his party for a generation. Under FPTP, the goal of the Conservative Party is to win around 35% of the votes and hope the Liberals and NDP both come in under 30%. The Conservatives count on FPTP vote splitting on the left to win elections. That's why they so desperately want to keep FPTP. If FPTP was replaced, the Conservatives would have to start appealing to at least half the voters to be able to form a government.