Reply to the message they actually sent, not the one you imagined they meant.

You read with your own worries attached, so a plain message can arrive carrying a tone nobody put in it. Then you answer the version in your head, the other person has no idea what they are being accused of, and an argument starts about something that was never said. Most online fights have this shape.

Before replying to anything that stung, read it once more looking only at what is literally there. Answer that. If you cannot tell whether a line was a dig, ask what they meant rather than responding to your guess.