Ancalagon
Dusty Dragon
This doesn't say that games where players don't play at least naively strongly shouldn't exist. But everyone who's saying they like playing sub-standard characters should by doing so be openly acknowledging that they play their own version of the game and that that is not and should not be the default for open groups.
I'll quickly make a small comment here: Not everyone has the choice of being an optimal character. I've mentioned once or trice here that I'm a swordsman. But I never claimed to be a great one - heck "fair" would be a bit generous. I'll never be a great swordsman - I don't have the reflexes, I haven't been training since I was a kid, and heck I don't have the joints for it either. It's not my choice.
Where am I getting with this? Well, sometimes people who are not swordmasters but merely decent combatants (in other words, not fully optimized) are trust into adventure. And these people can make very valid, even fun characters to roleplay.
4: Either I'm overconfident or I think they are overconfident. Or both. Unless they came armed for me personally, I think that we're a tougher nut than they expected to be able to crack and the mistake is actually theirs.
If they crack you, you are dead. Don't let hubris get you. Play smart

5: Because running is the single most stupid choice on the table. If we run we get hit in the back. And unless I'm playing the monk or the wizard they can run us down and put spears between our shoulderblades.
Historical battles had the majority of their casualties inflicted after the rout started. When instead of trying to advance against enemies with weapons in hand they were skewering the slowest in the back. Indeed, all else being equal, staying to fight the ambush is probably the smart tactical choice and running is a choice that will almost certainly get the slowest of our party members killed.
sigh - ok this is my bad. I've been using "run" as a shorthand for "withdrawal" or "fighting retreat" or whatever, *not* a rout. I should have written it differently, and I apologize. Running away willy nilly is indeed a *terrible* choice, and history certainly tells us this.
... Is that quote inverted? Because that seems to encourage running away6: It's better to live on our feet than die on our knees. And if I didn't make that decision I wouldn't be an adventurer.

7: I think they are bluffing.
See #4 - overconfidence?

8: They prepared the ambush - what on earth gives me the impression that the apparent obvious escape route is safe rather than another part in their trap?
Well... the way the party went through might also be a trap, granted. But the place the party is now is *definitely* a trap.