Adam asked [UPDATE: in a comment that was, alas, lost when we changed software two years ago] if suing the church might place one in the category of “groups that oppose the church.” He raises a question which, I think, does not have a yes-or-no answer.
My intuition is that the answer involves repeated use of the word qua. (See also here, third joke down, for the use of qua). To wit:
The church may be sued qua employer (put that aside for now). It may be in many other capacities. It may be sued qua tenant. It may be sued qua neighbor, or landowner, or contractor, and the list goes on and on. Finally, it may be sued qua church. The qua makes a difference.
Suing the church qua employer, tenant, neighbor, landowner, or contractor seems much less likely to trigger any membership problems. For example, if a church member is walking outside a church building and a negligently-placed brick falls and hits the member on the head, I don’t see why the member could not bring suit against the church. Likewise if construction on a new church building ruptures a water main and floods a member’s basement. And likewise if the church agrees to buy 100 suits from a member retailer, and then breaches the contract. The church may be a divinely-led organization, but it has a secular infrastructure which is not unlike any other infrastructure.
Separate from the secular infrastructure are church actions qua church. I may not bring suit for infliction of emotional distress when the Bishop tells me to repent. I may not sue the church over church policies which are divinely ordained (such as exclusion of women from the priesthood). Any such action would put me in the category of groups that oppose the church.
Finally, there are the mixed questions. For example, when the church is acting as an employer, it has a secular role, but may also be filling a religious role (and courts have upheld the religious aspect of church employment, see Corporation of the Presiding Bishop v. Amos. Whether Amos was rightly decided is a very complicated issue and beyond the scope of this post).
Those are my categories. From among those categories, it seems like baptism is a mixed question. It certainly has a religious purpose. On the other hand, I don’t think it is unreasonable to require that the church make baptisms be, as a general matter, safe events. For example, if the church were conducting baptisms in water next to downed power lines, and someone were electrocuted, suing the church could be a proper recourse. Since baptism is a mixed category, and since the challenged aspect here is a secular portion of baptism (the safety of the font, rather than the validity of the prayer), a suit is not inappropriate.
UPDATE [OLD]: I should have mentioned when I originally wrote this, that Gordon’s post about suing for breach of privacy in tithepayer status seems to be an instances of suing the church qua church, which is problematic. The case he cites, with a missionary who becomes ill, also appears to be suing the church qua church. (If the church were routinely exposing missionaries to highly unreasonable unsafe conditions, it might be different).
UPDATE [NEW]: This post refered to some comments which were, unfortunately, lost when we moved from blogspot to moveable type.