You raise an interesting question about symbols on temples. The pentagram is currently a widely used symbol in occult movements, but that is a recent development. It did not have those connotations when the Joseph Smith taught the LDS temple concept. The five-pointed star was used in the Nauvoo Temple and other early temples, but it's meaning was wholesome. Inverted stars did not generally become associated with the occult until after the time of Joseph Smith. For documentation, please see the excellent article by Matthew Brown, "Inverted Stars On LDS Temples," available at "http://www.fairlds.org/pubs/Stars.pdf. This article also shows that stars, including inverted stars, were used by early Christians as valid Christian symbols. The symbol of the star - whether it has five or six points - and the pentagram can be used for good or evil purposes. The fact that Satan worshippers have given evil meanings to the star, the broken cross, the goat, the moon, or whatever does not make the symbols inherently evil.
FYI, Bible uses the symbolism of heavenly bodies to describe the work of God. Specifically, the symbols of the stars, the moon, and the sun are used in describing the next life (1 Cor. 15: 40-42 and other places). Is it a shock to find the same symbols on some LDS temples, given that the temple is about preparing us for the next life? Further, in Revelation 22:16, Christ refers to himself as "the bright and morning star," and for early Latter-day Saints, the morning star symbol referred to the coming of Christ and His millennial reign - a perfectly appropriate symbol for the temple.
Similarity in symbols does not mean similarity in meaning. The cross-like Ankh symbol was used in pagan rituals of Egypt, but that does not make the symbol of the cross something pagan (though we prefer not to use the cross to remember Christ, wishing to focus on his victory over death through the Resurrection). If I walk into a cathedral and see a cross, it would be silly for me to condemn the Catholics for promoting pagan Egyptian rites with that symbol. The same applies to those who see stars, moons, or suns on the Salt Lake Temple.
I hope this answer helps, and I pray that you will continue looking into the Gospel.
This information is also available on my Mormon Answers page of "Slightly Facetious (?) Questions about Mormons and Mormon Beliefs."
Related post at Mormanity, Feb. 2011: "No, French Catholics Are Not Satanists: Understanding the Inverted Pentagram in Historical Christianity" - with photos of a French Catholic church with prominent inverted pentagrams displayed.
Also see SymbolDictionary.net on the pentagram, where we learn that it was used as an ancient symbol for Jerusalem and was used by medieval Christians to symbolize the five wounds of Christ. There we also read that, "It was not until the twentieth century that the pentagram became associated with Satanism, probably due to misinterpretation of symbols used by ceremonial magicians."