Just upgraded to Baron tier and got to try the Alpha, had the exact same question as you, heirofcarthage. Sorry to hear that it sounds like they won't consider a filter. I would just like to point out a few things.
1) No, cursing like this is not authentic. Was there cursing in medieval times? Absolutely. And an authentic game would need to represent that. But the phrasing and frequency of what's in the alpha are definitely based in a modern skew of a medieval setting.
2) Actually yes, several major game studios do in fact provide filters for their games. Look at any Call of Duty: Black Ops game. Look at the Gears of War franchise. Look at Brothers in Arms: Hell's Highway. All these games and more have utilized graphic content filters and each of these more are incredibly successful.
3) I work in games' development and no, editing content does not have to be difficult. I mean I guess it depends on how you approach the problem. If you're writing completely different lines and changing cutscenes, well then yes, that would be quite the undertaking. But there are other possibilities including adding/removing a particle effect, restricting camera movement, bleeping a word in an otherwise unmodified sentence, etc.
I acknowledge and accept that this game is targeted to adults. But several of us have different ideas as to what the words "adult" and "mature" mean. Some of us hear those and think of responsibility, duty, family...and some of us think of swearing and nudity. Hopefully what we can all agree on is that there is nothing immature about having different tastes. That's why I wish requests like heirofcarthage's to only create an option would get more traction, as it preserves the opportunity to have both tastes met. I feel that that insight would require a certain "maturity" on the part of more game developers though.