First: need doesn't play into civil rights. You don't need to have freedom of speech, religion, etc. And yet, these are your rights as a legal resident of the US. (Note that 2A rights are also rights for any person that is a legal resident of the US, including student visa holders.) Would anyone support licensing requirements prior to voting, shitposting online, or not having your house searched by cops on a whim? For anyone that thinks 'features' bans are a good idea, here's the judicial argument against them. Short version: if you can ban everything except the 'gun', because of how a 'gun' has been defined under the law, you can functionally ban guns, which undermines the entire point of having a second amendment. Maybe you think that's good; I would say that the entire history of gun control in the US disagrees with you, as it has always been used as a bludgeon against the black, the immigrant, the working poor, and anyone that doesn't have wealth, power, and privilege.
Second: an AR-15 is useful because:
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it's fully modular; you can easily customize it to suit your use-case. This is not true with most other rifles.
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They're cheap, and so are parts. Because so many are made, you can pick up one that's perfectly serviceable for about $500. In contrast, my carry pistol (CZ Shadow 2 compact) has a retail of about $1300 for the gun alone, not including spare magazines, optics, replacement grips, trigger parts, barrel bushing, slide stop, IWB holster, etc. My AR-15, all in, with optics, trigger, multiple magazines, replacement barrel, muzzle brake, etc., cost less than my carry gun. A Glock 19 g5 MOS and optic would run about the same as an inexpensive AR-15 and red dot.
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ammunition is cheap (for a rifle), and readily available almost anywhere. At about 40cpr, it's cheaper than nearly any other rifle ammunition.
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You have fewer issues with over-penetration as a home-defense weapon; the bullet tends to start tumbling as soon as hits drywall, and quickly loses speed. 9mm can have bigger issues with over-penetration in a home than 5.56/.223.
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It's more effective than a shotgun for home defense use, because it's more controllable, you have more shots before you need to reload, and it's easier/faster to reload. (Have you ever seen someone doing quad reloads on a shotgun? That's a skill that takes a very, very long time to master.) No, you don't have to just point a shotgun in the general direction of something; at home-defense ranges, shot spread is negligible. Most shotguns will also be longer than an AR-15, which make them less-ideal for more confined spaces.
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It's more effective than a handgun; a longer sight radius combined with more points of contact on your body makes it easier to aim and shoot effectively. And, again, you have more ammunition, which is a good thing when you're feeling deeply stressed. (Would an SBR AR-15 or a bullpup rifle be even better indoors? Yes.)
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They can be incredibly accurate; it's not difficult to turn an AR-15 into a sub-MOA rifle. A Ruger Mini-14 will never do better than about 2.5MOA.
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It can easily be chambered for multiple cartridges by swapping out barrels. With a different barrel, you can use a large variety of different cartridges, the most popular of which are .300BO, 6mm ARC, .400 Legend, .458 SOCOM, and .50 Beowulf.
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Plastic and aluminum pieces are less susceptible to environmental issues, e.g., they aren't affected by humidity and rot the way that wood is.
As far as the so-called "fetishism" goes - it's a tool. It's an effective tool, and often the best tool available. It's also an ad hominem attack; it says nothing about the tool, and instead goes after the people.