"Essential Christian beliefs are not affected by textual variants in the manuscript tradition of the New Testament."
That is a remarkable statement. We can, despite textual variation (mostly spelling differences and what not), trust that the New Testament we have now is remarkably close to its original written version.
Whether to believe what it says or not is up to you.
First of all, on your last sentence, I completely agree - people can choose to believe whatever they wish. On the essential Christian beliefs not being affected by textual variants....I also agree, for the cause of religious tradition and indoctrination. This accompanies the first point... people choose to believe what they wish.
On the point that the New Testament is remarkably close to it's original version....that is a belief people choose to accept as real or factual, based on ZERO evidence. Since there are no original manuscripts available for examination, it would be foolish to attempt to make any claims in their regard. You may hope to extrapolate from the earliest known and available writings of church fathers....but even that would provide a shadow of what actually was. What was originally written, and many case by whom, is unknown as it pertains to the bible.
On the work of Bart Ehrman, specifically Misquoting Jesus....what his work does demonstrate is that the New Testament as we know it is and has been a "work in progress" for thousands of years. He has shown that the text of the bible has been edited at will, by unnamed editors for hundreds and thousands of years. These editions include many changes to the text in many ways. These are facts that a person can research from themselves if they wish to, without even reading Bart Ehrman. Bible scholars have known this from quite some time.
The bible as it is commonly considered now, by Protestants is lacking some 14 books that used to be in the bible, and are still in some. Luther wanted to reduce it even further so that it would have less than the 66 books it has now.
The Catholics, and the Jehovah Witnesses, and probably more sects than I even know of have changed the text at will to suit their own church doctrines.
Modern translations of the bible, which come in some form each year, all make subtle changes to the text by word or phrase replacement. In some cases, these additions or edits have rendered the passage the exact opposite meaning of the original intent.
These are things that are known in the fields of biblical research and textual analysis, but not known by average Joe Q. Christian churchgoer. FWIW.