Because these clearly don't look like robots.
Clearly these robots - which are shaped suspiciously like humans for some reason - spew blood when you shoot them, and cry out in pain. (I'm working under the assumption that the guy with the 5-year-old daughter doesn't want all sound removed).
Personally I'm not bothered by the language - it's understandable in an M rated game - but I would agree that an option for people to turn it off would be a good thing.

However, the guy with the 5-year-old daughter is another matter, assuming he wasn't joking (oh boy is it difficult to tell on these sorts of forums sometimes)... I mean, really?
It's already been said but it bears repeating - you have a strange sense of what's right and wrong if swear words are a huge problem and running around shooting people and slitting people's throats repeatedly is not.
"Smart people" indeed.

It should be optional (without losing all speech). I have no idea why they felt the need to add this.

I agree,
While swearing was a cool feature when the demo first released, it quickly became old and annoying.
While I'm not saying that you should completely get rid of the trash talk, i think you should dial it down a little.

lol

I too, regardless of my own overfrequent use of vulgarity, feel that all the gratuitous use of intentionally foul language is just serving to dumb the game down to the level of Idiocracy (the movie). Players have headsets. They curse outloud all throughout the game, whether the game is rated M or rated E. Having the game automatically provide all these repetative verbal taunts, every single one of which is vulgar, is total overkill and makes me feel like I'm at a backyard wrestling match in some redneck town with a bunch of 15 yr old kids.

CRYTEK/EA, at the least, put in a "Toggle Taunts" option for us. I've only played the MP Demo for about 2 hours and I am already so sick of hearing these stupid lines that I want to mute the whole damn game.