Start by acknowledging the challenge without immediately surrendering the point. Then restate the evidence supporting your view and identify what new information would change it.

That creates a middle ground between being defensive and folding too quickly. You are showing conviction based on evidence, not attachment to being right.

Keep the tone calm and curious. Disagreement sounds much better when it is framed around the logic rather than the person. If useful, this guide on communication under pressure gives more detail.