If you join a group, and suddenly adopt the opinions/beliefs of that group, they may not be honest. The more in-depth/fundamental the opinion or belief is, the higher the suspicion of dishonesty is upon sudden change. Especially if joining the group provides you immediate benefits or it can be shown you tried to derive an immediate benefit through that group ownership.

It is certainly not impossible that one suddenly changed opinions and it had nothing to do with you trying to gain status within a new group (whether irl or social), but most people don't do that.