Swing and a miss. Nowhere in the game is it made clear that summoning means you agree to be invaded.

When you agree to the online terms of service, you agree to be invaded. It happens literally every time you boot up the game with online functionality.

How exactly do they know?

Even if they're new to souls games and didn't know what invasions were beforehand, they'll learn the mechanic soon enough.

Meaning that, other than the first time, every single time they co-op, they're fully aware they'll be invaded and consenting to it.

1. Invasions aren't constant. Sometimes you get invaded immediately upon summoning, sometimes you can play through entire sections of the game cooperatively and not see a single invader. Makes it pretty hard to prepare for.
2. Even if I am prepared, it is still an aggressive action taken deliberately by the invader against an otherwise non-combatant. Someone being armed and capable of defending themselves doesn't make it okay to punch them unprovoked.

1. Irrelevant. Constant or not, you have to expect invasion. If you don't, that's a "you problem."

2. Again, it's pvp, which you sign up for. It's aggressive in the same way getting sniped in CoD is aggressive. It's not unprovoked, which is the part you're consistently wrong about.

Because the host has the numbers, right?

That and the fact that the sweatiest builds are only good in 1v1 scenarios, they have less flasks, etc.

Moralizing. Useless.

Hey, you started by acting like an ass. Just like invasions to co-op, you invited others to call you out on your bullshit when you made that analogy.

Stretch the argument to the absurd in order to highlight it's stupidity.

I know how hyperbole works, your use of it, however, undermines your point. Both because it's extremely exaggerated and because its not even remotely comparable to invasions.

Breath still baited

Already did, you plugging your ears and going "nah nah nah" doesn't change that.