In the oral tradition there were verses of the same content that originated independently, which proves that in the early Islamic tradition these verses had already been widely accepted as part of the Qur'an. And there is even a passage in the Qur'an that Muslims use to deflect the accusation that Muhammed's revelations were false:
Sura 22:52-53 And We did not send before you
any messenger or prophet except that when he spoke [or recited], satan threw into it [some misunderstanding]. But Allah abolishes that which Satan throws in; then Allah makes precise His verses. And Allah is Knowing and Wise. [That is] so He may make what Satan throws in a trial for those within whose hearts is disease and those hard of heart. And indeed, the wrongdoers are in extreme dissension.
So basically God allows Satan to corrupt Islamic revelation for a period of time so as to test those whose hearts do not want to follow what is the truth. But I'm a little confused as to what they would understand to be the truth if Allow allowed Satanic revelation to come from his prophets' mouths. Also there is a similar passage that narrows the issue and focuses on Muhammed (in my opinion):
Sura 10:37-38 And it was not [possible] for this Qur'an to be produced by other than Allah, but [it is] a confirmation of what was before it and a detailed explanation of the [former] Scripture, about which there is no doubt, from the Lord of the worlds. Or do they say [about
the Prophet], "He invented it?" Say, "Then bring forth a surah like it and call upon [for assistance] whomever you can besides Allah, if you should be truthful."
So what you have is an admittance by the Qur'an that the prophets of Allah can speak the words of Satan, and an early Islamic tradition that arose independently from multiple sources claiming to want the intercession of three pagan goddesses. In terms of what faith I believe is more trustworthy, I think Judeo-Christianity is the more suitable candidate. But then again I tend to go with those revelations that are closer to the original source than those that arise hundreds if not thousands of years later.
And if you want to believe in the original revelations of God, then no one here is going to blame you. Muslims might, but they are only human. You don't need to fear their opinions. They only deceive themselves.
The process of compiling the Qur'an into its modern form was a lengthy and messy process that involved 1. oral tradition and memorization (of which it is said by some Muslims that they had forgotten the Suras), 2. the compiling of all oral traditions, the acceptance of some traditions and rejection of others, and 3. the burning of those copies that did not conform to the final renditions of the Qur'an. I have read parts of the Qur'an, and it is a very disjointed work that often skips between topics without any transition. And I think it all makes sense when seen in the light that the Qur'an was compiled from disjointed chapters and verses that different individuals had memorized over the years (and some had forgotten).