I am going to paraphrase Winston Churchill for you: "First past is badly broken. Except for all the others." Check proportional representation in Israel where parties with very few seats have outsize power because they tip the balance.
That's an interesting way to paraphrase him. He said, "Many forms of Government have been tried, and will be tried in this world of sin and woe. No one pretends that democracy is perfect or all-wise. Indeed it has been said that democracy is the worst form of Government except for all those other forms that have been tried from time to time.…" He was speaking in support of democracy, and proportional representation is a far more accurate implementation of democracy than first past the post. You literally paraphrased and changed his entire meaning.
He was also a rampant racist and is therefore hardly all-knowing anyway though. But I do agree with him about democracy.
If fringe parties have a toe-hold in the Israeli Knesset, it tells you that fringe views have a toe-hold in Israel. I also fail to see where parties with very few seats are tipping anything. Noam has 1 seat, for example, and is officially part of the Government, but even without that seat the Government still have a majority over the Opposition. In fact the swing is 8 seats, and only the two biggest parties in Government can cover that. The same is true in the Opposition. So the Government could want to pass a bill that Yahadut HaTora doesn't like, but make up those votes if Yisrael Beiteinu is in favour.
The only real reason to not want proportional representation is if you really like majority government. Almost certainly, in Canada, it would be a while before those who like the Conservatives today ever had the reigns again if we moved away from FPTP. But other conservative parties, who might be more progressive or moderate, might have a bigger say. Or rather the far right nutjobs might leave the Conservative party and it might stop catering to the fringe and become a rational party again finding itself come to favour. We'd also see new more left-leaning options, or even the Liberals shed some of the more aggressively left views. A centrist bloc might form out of these new Conservative and Liberal parties to dominate the landscape.
I wouldn't want the Sharia Law Party, or the Communist Party, or the Fascist Party running the show. But I'm perfectly happy letting them run in elections and draw votes away so that parties stop catering to them. If 1 seats worth of voters are fascist, then let the fascists win 1 seat. And then we'll know we need to focus on better education to get that down. Instead we have no idea how popular ideas are or where we most need work.
A lot of our government waste comes from elections that swing the party on power who then undo the stuff the last party has started at immense cost. Proportional Representation would likely give us more stability and eliminate that. It would also reduce the power of any one party meaning little pet projects that don't benefit anyone wouldn't really go ahead.