I come from a mixed Catholic/Protestant family and over many years have tried to reconcile these two great faiths, try to resist prejudices as expressed by either 'camp'.
To begin with, as other have said again and again, I have not found any Protestant hostility toward Mary. The prized role in a nativity play is that of Mary among Protestants. Ministers (sometimes joined by priests) hold Good Friday services at which someone always preaches on "John, behold your mother...."
The problem, of course, is that Catholics and Protestants see Mary differently. Permit me to sum up some of the common Protestant objections to the Catholic view of Mary.
1. Yes, Mary is blessed among women, as the Bible says. But where is there any suggestion of her immaculate conception? That doctrine was not defined until about 1870, during the Papacy of Pius IX, and many Protestant scholars believe that Mariology became more and more dominant in Catholicism starting with the 3rd century, influenced by various cults of the ancient world.
2. Where is there evidence that Mary lived a sinless life? Surely, there should be some reference to this in scripture. But scripture says that "all have sinned and fallen short....".
3. If Mary did not err (sin?), why did she and Joseph travel a day's journey from Jerusalem, not even realizing that their only son (and child?) was not with them?
4. If Mary was a perpetual virgin, what about Luke 1:25 - "and Joseph knew her not till she had brought forth her firstborn son, and Joseph called his name Jesus"?
5. And why use 'firstborn', as though there was a 'secondborn' etc., especially since elsewhere in the gospels brothers of Jesus are mentioned (such as Matt. 12:46)?
6. Oh, off the subject a bit, I always have been perplexed ar to why the genealogies of Jesus, in Matthew and Luke, tracing him back to David, both provide the family tree of Joseph and not Mary. Why? And have you noticed how much those two genealogical accounts are in conflict with one another? Matt, 1:1-16 and Luke 3:23-38. And the years between Abraham and Adam (in Luke) are suspect when we compare them to what science and history tell us. How do Biblical literalists, Protestant and Catholic, explain such contradictions?
7. Why does Jesus even seem somewhat dismissive of Mary in her only two appearances in the gospels between the visit to the temple and the crucifixion - Matt. 12:46-50 and John 2:4? "Who is my mother...?" "Woman, what have I to do with you...."
8. Why, in all of his letters, doesn't St. Paul once mention Mary? He was the key evangelist and adviser to the early churches, instructing them in the major beliefs of Christianity, but writes not a word about Mary? The same is true of other epistle writers in the New Testament. Some find references to Mary in Revelation, but that is highly controversial. Anyone who can provide a seriously authoritative interpretation of Revelation merits some major award.
9. Why isn't the assumption of Mary mentioned in scripture and not defined until Pius IX in 1950?
This is not to show disrespect for Mary. But to Protestants Mariology has escalated to the point where it seems independent of scripture.
Can't Christians honor and love Mary without making her the 'Queen of the Universe", designating her as Our Lady of nations, professions, the seas and mountains, the air and much more, crowning her statues, and in many other ways seeming to worship her? The claim is made that she is not worshiped, but when the 'Hail Mary' is the most popular prayer among Catholics it seems reasonable that non-Catholics will wonder. True, the first part of that prayer was stated by Elizabeth, but the rest is not from scripture.
Having said all this, I personally don't care that Catholics and Protestants differ on Mary. I believe in 'big tent' Christianity were the faithful with various views are welcome. God is interested in our hearts - our faith, our love of him and one another - and not in our creeds or church affiliations. I know that millions of Catholics have been raised to venerate Mary and they find enormous comfort in this. Fine. And Protestants are raised to appreciate Mary but not venerate her. Fine, also.
God bless all his children, of every creed, color and country. May religion become a bridge rather than a barrier. I'm sure Christ would favor that.