A handful of prominent evangelical activists are defending their decision to attend television host Glenn Beck's conservative rally in Washington this weekend after some Christians complained that evangelicals shouldn't be partnering with Beck because of his Mormon faith.

Video: Glenn Beck rally stirs controversy

"There is no need to 'de-Christianize' each other over the matter," wrote Jim Garlow, an influential California pastor, in a five-page memo this week arguing that evangelicals can attend Beck's rally and partner with the television and radio personality in good conscience.

"Glenn Beck is being used by God - mightily," Garlow wrote in the memo, which was obtained by CNN. "The left loves to slam him and do so viscerally and often with vulgarities. Glenn is not perfect... But his expose on America's sins is stellar."

Garlow - who partnered with Mormons in California to help pass Proposition 8, the state's gay marriage ban, via ballot initiative in 2008 - is one of several high profile evangelicals on the defensive about participating in Beck's rally, called Restoring Honor.

The rally, which is to be held near the Lincoln Memorial on the 47th anniversary of Martin Luther King Jr.'s "I Have a Dream" speech, is to be headlined by Sarah Palin.

Christian critics of the event have taken specific aim at some evangelicals' participation in a prerally event Friday at the Kennedy Center called Glenn Beck's Divine Destiny.

Beck, who many evangelicals say is not a Christian because of his Mormon beliefs, says on his website that the Friday event "will help heal your soul."

"Guided by uplifting music, nationally-known religious figures from all faiths will unite to deliver messages reminiscent to those given during the struggles of America's earliest days," his site says of the event.

Brannon Howse, a conservative writer and founder of Worldview Weekend, which organizes Christian conferences, criticized evangelical participation in that event in a column this week.

"The Apostle Paul warns Christians against uniting with unbelievers in spiritual endeavors," Howse wrote. "While I applaud and agree with many of Glenn Beck's conservative and constitutional views, that does not give me or any other Bible-believing Christian justification to compromise Biblical truth by spiritually joining Beck."

Much of the criticism - along with confusion about the propriety of evangelicals politically linking arms with Mormons - is less formal and more rooted among in-the-pews churchgoers than evangelical elites.

"Jesus Christ's Church has universally rejected Mormonism's Anti-Trinitarian theology and its claim that mortals may become God," David Shedlock, a contributor to the evangelical blog Caffeinated Thoughts, wrote in a post this month. "Beck asks Christian leaders to 'put differences aside,' but Beck himself daily peppers his broadcasts with Mormon distinctives because he cannot keep his beliefs to himself."

Evangelical defenses of attending the Beck rally are largely aimed at ordinary evangelicals. Garlow circulated his memo in an email titled "In case some criticize you for attending the Glenn Beck Rally – since he is a Mormon."

Many Christians say that some Mormon beliefs, including that Mormon church leaders are prophets and that the Book of Mormon is sacred scripture, are incompatible with Christianity.

Mormons, though, consider themselves Christian. The Mormon church is called the Church of Jesus Christ of Latter-day Saints.

Many conservative evangelical activists argue that evangelicals and Mormons should set aside theological differences to partner on moral and political issues.

"For Christians concerned about Glenn's faith, I would ask the following questions: What fruit do you see produced by Glenn," David Barton, an influential evangelical activist who is joining Beck's rally, wrote on his Facebook page recently. "Good or bad? If you judged Glenn only by the fruits he has produced, would you still hold concerns over his faith?"

"Christians concerned about Glenn's faith should judge the tree by its fruits, not its labels," Barton, a former Republican National Committee consultant, continued. "After all, Nancy Pelosi and Bill Clinton openly call themselves Christians... Although these individuals have the right labels, they have the wrong fruits."

Other evangelical activists have gone further, arguing that Beck's faith isn't that different from that of mainstream Christians.

"I have interviewed persons who have talked specifically with Glenn about his personal salvation - persons extremely well known in Christianity - and they have affirmed (using language evangelicals understand), 'Glenn is saved,' " Garlow said in his memo, which was dated Wednesday. "He understands receiving Christ as savior."