I don't think that's an easy 'yes' or 'no', and the best answer might be 'later'.

If this is the best outlet for physical exercise, I'd make him participate.
If you are right that he doesn't like team sports because he hates to lose, this is a good learning opportunity.

At 6, he may not be ready for team sports, GS10 was not. My DS, at 6, was not.