Just a word on some people's propensity to attribute the reason for another's views to the fact that they were once a Protestant. I liken this to someone once having spent time in jail. He was convicted, has paid his dues, and has been many years living as a law abiding citizen, but he is still referred to as a convict. Once a convict always a convict?
If a person presents views or doctrines that are not in keeping with the mindset or doctrines of the Church, then speak to the issue at hand. To refer to their former Protestantism is to call them a convict. Once a Protestant, always a Protestant? This is almost always received as a slam or a denigration of the person and does nothing to promote right thinking. Such an approach is subjective. How long must one have been out of prison before he is deemed no longer tainted?
I have been out of Protestantism for over ten years. I am quick to embrace the doctrines and traditions of the church. If there are things I don't yet know, it is because I have not yet learned them, not because I once was a Protestant. There are some Orthodox clergy who have come from Catholicism and have been away from that world for less time than I have been away from Protestantism. Is it fair for me to hold them currently suspect because of their past? Once a Catholic always a Catholic?
Last time I looked, God is a God of redemption and restoration. "He casts our sins as far as the East is from the West and remembers them no more." It is totally appropriate and sometimes necessary to point out that a proposed belief is particularly a Protestant one or a Catholic one, but God forbid the kind accusatory language in our interpersonal communication which makes a person's past the issue.
UPDATE Addendum: Please see Tserkovnye Vekhi's thorough and blessed perspective on this matter in the COMMENT section.