People often hear tone before they understand content.

Tone is processed first and it colours everything after. By the time your reasoning arrives, the listener has already decided whether they are being attacked, dismissed, or spoken to fairly, and that judgment shapes how the content is heard. A good argument delivered with an edge is heard as an edge.

Before a difficult exchange, take a moment to settle your own state rather than rehearsing your points. The words matter less than the register they arrive in. If you cannot manage the tone yet, that is a strong argument for having the conversation later.