Just a couple of quick opinions here.
If you accept governmental funds, you are subject to governmental oversight and rules. No exceptions. This goes for parochial schools and religious-run businesses and hospitals.
If you are a house of religion and claim tax-exempt status for it, using the church to further business or governmental interests is breaking the covenant that allowed you to be free from taxation. Giving inflammatory sermons and then sending them directly to the IRS to dare them to do something about it just to get press for it is not what Jesus would do.
Then again, when asked about taxation, He said “Then give to the emperor the things that are the emperor’s, and to God the things that are God’s.” [NRSV translation]
If school vouchers may be used for religious schools, they may be used for schools of all religions. To limit it would be discriminatory. But a religious school that accepts them falls under governmental guidelines, as earlier stated.
It is OK to wish someone Merry Christmas, Happy Easter, Blessed Samhain, Happy Hanukkah, or whatever the appropriate greetings are for Ramadan, the festival for Ganesh, the holidays of Santeria or any of a thousand other religions. We don’t have to scrub all religious references from the world to live in harmony. That’s what diversity is for. We celebrate it and learn from those who are different what they worship and grow from the new experiences. If people want to use their personal time and funds to decorate their office for a holiday, even if it is a governmental office, more power to them. Just don’t use governmental funds to buy religious decorations.
And the final festival day for Ganesh is wonderful fun. If you haven’t seen Ganesh thrown in the lake/river/ocean, ask a Hindu friend if you can join next fall. And if you hadn’t heard (I just recently learned this), Hinduism is not polytheistic. They just have one god. That god just has many aspects, each of which has been given a name. Christians have one God. He has three aspects: Father, Son, and Holy Ghost.