Who (liberals or conservatives) tend to think the Establishment Clause allows government to accommodate religion so long as it does not force anyone to participate in religious activities against their will and does not promote one religion over another?

Liberals.

Explanation:

In the liberals theory, no one should have any saying on other's people belief. Liberals believe that the government should be as minimun as possible, not intervening on people's decision on how they life their life's, as long as it doesn't affect on other's people life. That goes from economic decisions, based on lower taxes, to religions matters.