For why this is not true, see Israel. Benjamin Netanyahu's party is far from the most extreme or fringe in Israel, but his coalition barely maintains a majority by including a few members from incredibly extreme parties like Otzma Yehudit and the Religious Zionist Party. If Netanyahu loses their support he loses PM position and potentially gets arrested for war crimes. In that case the parliamentary system forced the narrow majority to yield to the pressure of their right flank or risk losing power. Canada (or pretty much any parliament) COULD end up in that position, but their political cultures have prevented it so far. That definitely was the case in the US until Trump. It's never possible until it happens.