Sticks and stones may break my bones, but words will never hurt me.
I call Baloney on that childhood rhyme.
I want to use a simplified model of communication in this post: two people talking to each other. When Alice speaks, she has intent. When Bob listens to her, her words have an impact on him. Good communication happens when [good] intent has a matching impact. When the two don't align (as can be a problem for relationships, religious beliefs, and more), those words can get offensive. (Seriously, read It's not about The Onion.)
If the intent is good, but the impact is bad (sorry, I'm still simplifying), I need more information. Does Alice know her impact is bad? Has Alice actually been told this? Has Alice apologized, sympathized, or empathized? Has Alice thought about how to do better in the future? If the pattern of behavior is all bad impact with no visible effort to improve, it's just toxic waste [see #6].
Intent and impact are two sides of the same coin of communication.
I think intent does matter, but it's not the only thing. In a conversation with two equal participants, Alice's intent should have an equal weight compared to the impact on Bob. If Alice exhibits a pattern of undesirable impact that she hasn't improved (even if bungled), I personally care a whole lot less about her intent.
UPDATE: Scientific American has a thoughtful blog post on intent versus impact titled "But I didn’t mean it!" Why it’s so hard to prioritize impacts over intents.