The reason why he says matters, there are many situations in which the tooth to be removed,
1. For midline adjustment
2. For occlusal settlement
3. For periodontal issues
4. Untreatable carious tooth and many more reasons.
Next Steps
It is better to discuss with him why it should be removed, and then proceed.
Health Tips
Please don't discontinue the treatment, or alter the treatment plan by yourself. It will create futher problems.
Hope this helps you sir