When people talk about corporate welfare, what they really mean is that the government is giving these entities so many tax perks it amounts to free money (unless we are talking about agribusiness and the military industrial complex). So, we as a country have an inate understanding that government subsidizes certain industries or behaviours through the tax code. People get to deduct contributions to churches. Churches pay no tax, and clergy recieve massive tax perks. This is an indirect way for government to establish religion in this country. Imagine for a second how successful many churches would be if they actually had to pay tax, or had to audit their books. I don't think anyone would argue that churches would suffer from refusing a religous contribution deduction, let alone the freebies given to clergy and churches. If an entity cannot continue without a given government policy, it seems to reason that the government policy is enabling its existence. Isn't this the entire thing the establishment clause was designed to prevent?