Actually no, it doesn't work that way,
Area spells ( blessings ) doesn't affect those who are unfriendly or enemies to the caster deity, it is as if the unfriendly/ enemy was not there in first place. As an example a Toranite surrounded by a corathite , an ilsarean and a Berylite, casting Mass heal, he only would benefit on the spell even if they all are on the area.
Also there are some druids that have their deity field filled as well, devoting their druid point of view to comune with the views of the deity ( not to mention that a druid might not be "neutral" towards everyone,. Face a druid with this argument after raising an army of undeads and you'll find fast at the tip of severe call lightnings to say the least )