Why Is It, That When I Tell People I'm LDS Or "Mormon" Their Opinion Of Me Instantly Changes?

To understand that reaction (and it's not just you, it also applies to Pentecostalists and especially Jehovah's Witnesses), you should read comparative religious studies, and see how the tenets of Mormonism differ from those of other Christian sects. Consider how members of your faith regard others, read about other non-Christian religions, and decide for yourself what makes most sense of the world and your place in it. To have contact with only those of a narrow and somewhat extreme faith is not a good thing, and it's noticeable that many of those sects are highly exclusive, i.e. Everyone's going to Hell but us, and they have strict controls against members venturing outside their doors. Shunning is a great sign of weakness in any faith.

First I would like to say, Greetings from the Lord Jesus Christ! I too was once a LDS member, and I remember being told when I first joined, that I would be persecuted for this religion. And soooo true and right that was! I would tell one person, outside the church and some how it seemed the whole neighborhood would know and treat me badly. It even got so bad, my husbands pastor came from his church, because my husband quit going (his choice), but he was not apart of LDS. The pastor told me I would burn in hell for being apart of that church. I was so much more determined that this religion was true. Do you read the Holy Bible that is apart of the Book of Mormon, Doctrines and Covenants, and Word of Wisdom; four in one book? Any way, the Mormon book actually encouraged me to read the Holy Bible for myself, because I was taught that the Mormon and Bible are one. I read this verse: Know this also, that in the last days perilous times shall come. For men shall be lovers of their own selves, covetous (wanting something so bad it makes you unhappy), boasters, proud, blasphemers, disobedient to parents, unthankful, unholy, without natural affection (for God made them man and woman), promise breakers, false accusers, incontinent, fierce, dispisers of those that are good, traitors, heady, high minded, lovers of pleasures more than lovers of God; having a FORM OF GODLINESS, but DENYING THE POWER thereof: From such turn away. They are the kind that work their way into people's homes and win the trust of vulnerable women who are burdened with the guilt of sin and controlled by various desires. EVER LEARNING, AND NEVER ABLE TO COME TO THE KNOWLEDGE OF THE TRUTH. 1 Timothy 3:1-7

I too shrugged this off, but after days, weeks, months of persecution and seeing really messed up things (become my friend to know what), my sister was very supportive, I even sent her all my pamphlets and the Book of Mormon for herself; she said something to me that opened my eyes from then on. She said, "the devil can be deceiving".
That woke me up out of my trance I must have been in: I thought, hmmm, they do not speak much of the devil, except for before baptism the devil will try to change my mind. I had had doubt for months (couldn't get baptised, b/c I couldn't fully quite smoking cigarettes, i.e. By the grace of God I no longer smoke). My doubt would become overwhelming at times, I didn't know what to do, but I confided in my home visiting elders.

In conclusion, I understand exactly what you are going through, but God is the only way, the Holy Bible is the truth, not any other doctrine.

Please, look at my profile and become my friend, I will tell you much more!