1) Same reason muskets trump trained knights and longbowmen. Even though heavy plate was actually effective against primitive firearms, and longbows worked more reliably and with excellent range, you could kit out a peasant with an arquebus for much less than the cost of mounting and armoring a knight, and a fraction of the training (you had to train for years to be able to fight effectively in mail or on horseback and drawing a longbow was an elite skill that required extreme muscle hypertrophy. It took a few hours to learn how to operate your firearm, and a few weeks to learn how to coordinate with other peasants.) Similarly, even if wizards were significantly more lethal and/or survivable than dudes with carbines, they'd be incredibly outnumbered.
2) In the Harry Potter World, combat magic is really weak. It's almost all short range and slow, often nonlethal, rarely provides area effects, and nobody really trains it. Automatic weapons have cyclic rates of hundreds or even thousands of rounds per minute, and trained operators can hit a target at half a mile or more. And that's just small arms. They wouldn't even need special anti-magic weapons, unless the wizards were extremely well organized.
With regards to (2), I think you’re confusing first-year war games with actual combat magic.
Actual “I really want to kill you” spells are probably much more powerful. Fiendfyre for example has at least the destructive potential of a tank, and in canon even Goyle could cast it. (It’s hard to control, but then again so is a tank.) Avada Kedavra can probably kill you even through a nuclear bunker wall, and it can be used by at least some teenagers. Sectumsempra is probably a instant-kill against a muggle, even with body armor, and it was invented by Snape wh...
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 97. The previous thread is at nearly 500 comments.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system.
Also: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: