Your friends don't know how to play fighters. Apparently, neither do you.
Tell me something I don't know about fighters, then.
Grapple checks? Knockdowns? Bull rushes? Whirlwind attacks? Arrows?
Fighters hit things until they die. End of story. No tricks. The only tricks they have is in their equipment and their potions. It is impossible to play a fighter and beat any caster that's worth a lick of salt. Planning on trying to cripple me in melee somehow? Good luck actually hitting through my thousands of mirror images, buffed armor class, and damage reduction. Going to try and dispel my stuff through the use of an item? That's too bad; I've got a spell mantle or two up that'll absorb it. Actually, fuck all that. I'll just Dire Charm you right away to make you MY meatshield.
Don't tell me I don't know how to play a fighter. That's pretty insulting.
The way Pen and Paper is designed, you're pretty much only supposed to have one significant encounter a day. Fighters are nice buff targets for a party or good to take a few levels in if you want some quick fighter-oriented feats, but that's the end of their purpose. They're good for campaigns where you slog through lots of meat, as well, because they have longer battle endurance than casters. I'd still just rather have a cleric or druid tanking, however.
It sounds to me like a lot of this comes down to the campaign you're playing in. What's your wizard going to do when ambushed or otherwise not allowed to prep (happened in the last two encounters in the campaign I'm playing in). What's your wizard going to do when the enemy has hella spell resistance (last encounter). Fighters are good in different situations from wizards. If you're at range with a good meat shield, then yeah, you're right, you're going to win with a caster.
As for "they hit things until they die", three of the 5 things you mentioned in your list are nonfatal; quite useful when you need to catch a fleeing person and interrogate them. High strength is useful for climbing, swimming, opening, breaking things, etc... High HP lets them take point in case of ambush, or a trap the rogue missed (and the DCs on decent traps are so high, they will be missed), or to cover the squishy caster behind them. High fortitude saves cover those pesky death spells and poisons (Rogues are just no fun as a caster, and Assassins even less so). Along more campaign-specific lines, there's certainly a long history of warrior cultures who would respect a fighter and fear/hate/scorn a wizard (just as there's plenty of examples of magocracies that feel the opposite way).
As for mirror image, buffed AC, and DR, well, let's see... generously speaking* you'll have about 20 AC or so at mid levels, and certainly not more than 10 DR. Honestly not that hard to get through either of those, and you don't have much HP to back it up. To deal with the mirror image, we'll whirlwind attack and/or cleave. For mind-affecting spells, protection from evil does a great job, and is not that difficult to get a means of using.
All that said, I play casters myself. Generally not your typical combat power caster though. My last character was a cleric/fleshwarper focused entirely on self buffs (died on Friday, largely due to not getting prep time :/ ). The one before that was a pacifist sorcerer/bard.
*this is assuming a non-munchkin wizard of course, and campaign power levels similar to what I'm used to. I'm sure it's possible to build one that throws these numbers way off.