Actually, they looked at the frequency of elections over the last 50 years in western democracies that use FPTP vs PR. They found that on average FPTP governments conducted more elections than PR governments.If you think for one second that any form of PR (which STV Isn't really anyway, but...) produces more stable minority governments: All I can say is "Isreal", look it up.
And Israel uses a pure list system, not STV. To say that Israel is representative of all PR governments is akin to saying India (which has a coalition of 18 parties) is representative of all British Parliamentary governments (ie, Canada, UK etc.).
Additionally, this ignores all the other, stable PR governments like Ireland (their last three minorities have lasted 5 years, try getting a majority in Canada to last that long), Germany, Denmark, Iceland, Australia, Belgium, etc..
Actually, over influence of fringe parties was one of the many aspects taken under consideration and one of the reasons why the Citizen's Assembly, 160 citizen's from all walks of life, who voted 95% in favour (so you claim that each and everyone of them thought the fast ferries were a good idea? Interesting), chose STV. Because it works with preferential ballots.Also, yes with FPTP the IRA wouldn't have gotten any terrorists elected. I guess you think that would be a bad thing?
Do we REALLY want the Pot Party and the Communist Party to have seats? What about the Rhinos?
With preferential ballots, a candidate that doesn't get elected right off the bat, but is still in the running, will need the votes of his/her opposition to win a seat. So he/she will need to convince the voters of the opposition candidates to consider ranking him/her as a second or third choice. This won't happen with fringe parties because they generally only appeal to their core supporters. STV rewards candidates that have more inclusive, more broad based appeal.
Finally, the threshold that a single candidate needs to win election is around 15,000-20,000 votes. Fringe parties like the Communist and Sex Party only have around a few hundred votes in total; there's no way they could make up that gap. The Marijuana Party got 11,000 votes, but that's also spread across all of BC so they wouldn't come close either.