I'm a Christian and I go to church every Sunday. My pastor is doing a series now on what it means to be a Christian and a citizen of the United States. He has never endorsed a candidate, and has explicitly said many times that his job isn't to push people to make certain political decisions.
So, "Pulpit Freedom Sunday" is misguided. The participants claim that their free speech rights are being violated because pastors can't endorse political candidates while simultaneously operating their churches tax-free. They want to have both, but why should they expect to? Being exempt from taxes and being able to receive tax-deductible donations is a pretty huge subsidy, so it isn't particularly offensive to me that society asks something in return.
The strongest argument in favor of the "Pulpit Freedom Sunday" protest is the fact that public employee unions are 100% funded from tax dollars (forcibly passed through public employees) and are still allowed to endorse candidates. Why not level the playing field and prevent all taxpayer-funded organizations from political activity?
As for the pastors participating in this protest, I think they'd do best to focus on sharing the gospel and God's Word. Jesus certainly engaged with the political leaders of his day, but he always kept his eye focused on winning spiritual victories.