Say thank you.
Do not argue or rebut it, a reader's opinion is not wrong. If they didn't "get" what you meant, there's a possibility you wrote it wrong. If more than one reader crits the same issue, the possibility you wrote it wrong increases. Accept the crit and fix it, or ignore it, that is your choice. You are not obligated to fix every little thing, though it would be foolish to dismiss it without thinking about it first.
But always thank your critters for their time.