What's Wrong with the Liberal Movement in Utah

I got an email from the Alliance for a Better UTAH this morning that started with this: 

"We are tired of the Sutherland Institute and Eagle Forum holding politics and politicians of Utah hostage to their close-minded, bigoted views. They continue to dig in their hills on issues that should be no-brainers..."

I replied with this: 

No offense, but you could use an editor. I don't think they dig in their hills, unless they're looking for gold. They dig their heels into the ground to slow down whatever horse is pulling them along. 

Within a few short minutes I got this back: 

No offense, but it IS a correct idiom:

dig one's heels in
Fig. to refuse to alter one's course of action or opinions; to be obstinate or determined.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs

or

dig your heels in
to refuse to do what other people are trying to persuade you to do, especially to refuse to change your opinions or plans
Cambridge Idioms Dictionary, 2nd ed. 

My reply to that: 

Exactly my point. But the text says, "They continue to dig in their hills..."

Their reply: 

We just realized the misspelling you were referring to, not an incorrect use. Unfortunately, we're human and occasionally mistakes happen.

And my second to last reply: 

I figured it was a misspelling, probably an autocorrect error, which is why I suggested using an editor. I really didn't mean to offend. I've learned from experience that when something like that jumps out of a communication, particularly at the beginning and especially when it appears to be a misuse of a common metaphor rather than a typo, it tends to lower the credibility of the whole message. If it came from my shop, I would make the correction and resend it. 

And a PS: 

PS This one is debatable and commonly used both ways, but I would also change "close-minded" to "closed-minded," because the mind is closed rather than close. Sorry to be a nuisance. I will stop. 

I tend to agree with some of this group's issues, but I can't support a group (the email was soliciting donations) that reinforces the stereotype of angry liberals who speak before they think, and when you give them a logical argument, they ignore the argument and shoot again without thinking. Then when they realize their error, they will not admit that they made an error. Notice that it was simply a misspelling and not their usage. And it's not that they occasionally make mistakes; mistakes just happen.