I've used Norton AV (not even the full suite, just AV) forever, which for me on line means back to 1999 or 2000, and I've never had a virus or other malware. I know nothing has slipped by undetected because my techie friend has done security sweeps on my rigs whenever any repair work was needed, with some very sophisticated tools, and always came up clean.
It has on occasion quarantines gauges, sometimes quite a few, though never anywhere near all of them, and I had to restore them one at a time, but in around eighteen years that's only happened two or three times, and not for quite a while.
It also sometimes warns me that brand newly released aircraft or scenery downloads are suspicious because they have few users, but that's OK, it just lets me know that Norton is paying attention.
Very interesting about Peter Norton! Interesting tidbit about M$ too, somehow not surprising.