Serena Williams now baptized as a Jehovah's Witness

[C_T_Russell]

There must be a bit of competition between the JWs and Scientology to attract all the high profile stars...

It certainly does appear that way.

If a friend or family member of mine decided to join a religious organisation and as long as they didn't bombard me with there ideology about it and as long as they wernt being harmed or harming others I would say go for it because its their business not mine.

Yes exactly - as long as they're not harming anyone & it meets their need for a belief system, then its their business. And there's always the chance that at a future point they might change their views.

It might not hurt you or me, but it affects lives around them if they are indeed following their rules.
After I left, all my family and friends cut me off, but it can go the other way round too. Lots of members who join the religion wi cut off their family who are not members.
When you go knocking on doors and potentially converting someone, you are inadvertently ruining another person's life indirectly.
Thankfully I never had any luck converting anyone when I did it, I never really put much effort into it like many do.