Whether or not they appear in the earliest manuscripts is not necessarily the issue. The issue is, are they authentic?
I'm an author, not a serious one, but an author none-the-less. Everyone knows that authors may sometimes update their information to include other information. Who is to say that Mark did not add that information in a later edition and both editions continued to be copied?
I do not think that you can de-authenticate the verses just because they did not appear in the earliest manuscripts. You must give proof for your accusation. So can you tell me exactly who added them? You may then have substance to your argument.
AndOne, I just read your George Whitefield quote and found it amusing since I totally agree with him. Too much can be made of the will of man. He has one but it is of precious little use to him if he use it wrongly because only Jesus can save. What is also true is sin is our DNA. We hear so much about how powerful our DNA is these days it is better to trust God to turn us. He turned me. Once the Holy Spirit showed me what he had already done the decision was easy. I did, however, make a decision but I would have to say it was not really my own. I simply had no argument left and never looked for one.
I don't know what an Arminian is supposed to believe, nor a Calvinist for that matter.