If you're offended by just the initials, then, WTF.

W-Why
T-That's
F-Frustrating
No, not offended. Just a bit of an observation that WTF seems to have become part of our present day language for Frustrated individuals. In most cases, it really does not add to a Post and is not really necessary.
Perhaps, being of the older generation, (read Old Fart), who learned to communicate using the Queen's English, if you can not get your point across without using profanity or agressiveness, then the point does not really have too much validity to begin with.
Although I am sure that the original WTF post stood for other words, I do like your WTF of "Why That's Frustrating."
I think we tend to forget that we GunNutz are not the only ones who read these posts and threads. With the Anti-Gun crowd acting Rabid and trying to deprive us of our posessions and enjoyment, these people are only more than happy to point out that we are a bunch of foul mouthed, crazy, incompetent, dangerous, or any other description of us that will further their views. And some of these posts only provide ammunition for them to use.
Not to mention the Ladies, Children and ordinary people who look at the GunNutz and other firearms related sites.

Can you picture the 8 year old who comes to the table and says, "Hey Mom, WTF is for Breakfast?"

and the explanation "But Mom, I learned that on GunNutz!"
However, WTF is a handy expression that you can THINK when you are confronted with occurances, like "Honey, WTF were you thinking about when you drove the car into the back will of the Garage?" or you boss's latest ideas; "WTF is this Idiot trying to do now?"
.