Fortunately, in the four months this site has been up, this is the first time we've seen the word heresy. (Well, second if you count this answer which notes that Pelagianism has historically been considered a heresy.) However, it's not the first time I've seen users taking such an aggressive tone against people with whom they disagree.
Left unchecked, this aggressiveness will drag down the site and destroy it before it gets out of beta. My vote is to delete these answers or questions, because I don't see how anything less could possibly keep the tone civil.
@Ray and Dan have suggested handling this with downvotes and comments. I'd like to believe that would make a difference. But so far (admittedly, from a sample of one) that does not appear to be the case.
The answer we're discussing has, as I write this, six upvotes and two downvotes, and is the accepted answer for the question. That's good for 71 points. That doesn't look like a deterrent to me.
The original answer used the controversial phrase "heresy of feminism", and after much community discussion @LanceRoberts edited the answer to remove the word "feminism". That's a good start. However, the word "heresy" remains, although what it's referencing is a bit more vague.
By giving positive feedback to answers that include the word "heresy", we are creating an atmosphere where people who agree with that viewpoint feel more welcome, and people with other viewpoints feel less welcome. Eventually, Biblical Hermeneutics will have an orthodoxy, and all of us who don't adhere to it will be "heretics".
Edit: I can see I wasn't clear. The issue isn't name-calling. The issue is setting expectations for which points of view are welcome here. Maybe a hypothetical example would help.
Suppose someone asked a question about the authenticity of the "Comma Johanneum" in 1 John 5:7. Suppose, too, that one answer was from a Jehovah's Witness, and included a paragraph near the end that said, "The Comma Johanneum has often been used to support the false doctrine of the trinity." And finally, suppose that the quality of this answer (minus this doctrinal statement) was such that it became the highest-voted and accepted answer. Some visitors to the site will see this answer and assume this is a Jehovah's Witness website; if they are JW themselves, they may be more likely to stay, but if they are not, they may be more likely to leave. Over time, the readership will skew more toward a JW point of view, and the initial erroneous impression of the site based on the phrase "false doctrine of the trinity" will become an accurate picture of the site's focus.
Suppose, however, that the phrase "false doctrine of the trinity" was deemed offensive by many users, and the user changed his answer to read, "The Comma Johanneum has often been used to support false doctrines." This is no better just for being less specific. It will still be clear to many readers just which doctrine is being referenced.
Likewise here. The phrase "heresies that denigrate the biblical concept of male headship" is hardly different from "the heresy of feminism". It's still obvious that the same concept is being referenced. The end result is that the site will gradually skew toward a Complementarian point of view.