Think about how atheist groups respond to Christian proselytizing on high school and college sports teams. In general, we send letters warning teams why this is a problem at secular schools and remind them they must keep everything religiously neutral.
That’s it. We don’t say “you must promote atheism.” We don’t say you can’t proselytize off the field. But when coaches are on the clock, they shouldn’t be preaching or using the opportunity to promote their faith.