Yes, the schism within the Christian world is of great concern to me, and the downside of Protestantism is the lack of unity and the myriad denominations. But for me, as it was with Luther, is a matter of reason, conscience and faith (meaning guided by the Holy Spirit) that I am a Protestant.
My reason and my intellect tell me that all of Marian doctrine has no basis in history or early tradition. My conscience and my faith tell me that it is blasphemy, according to scripture, to attribute to anyone other than Christ the atoning work of redemption. And my reason, conscience and faith tell me that praying to anyone other than the Trinity is idolatry.
Except of course those mainline protestant denimonations that cater to the feminists who insist that the trinity be refered to as "Creator, redeemor and sanctifier".