You actually clicked on the 'Completely Agree' icon for a post that accuses the the Shia of outcasting converts who are not Shia! How do you justify that? You know that claim is a lie.
That poster said the following, and you 'Completely Agree' with it: "you people are being arrogant and bullies, and Allah hates the oppressor and the arrogant ones. You people are hurt because your master (shaytan) is upset when Tate spreads Islam".
You agree with someone who accused your fellow Shia of being arrogant and bullies and having Shaytan as their master? Those are grave accusations and agreeing with them is not benign matter.
Your post is a misrepresentation of the issue. We don't condemn him simply because he did sinful things before he announced his conversion. Many converts did sinful things and you don't see us condemning them. It is the nature of his actions after conversion and the nature of those past actions that concerns us.
For the sake of argument let us assume that he is only being condemned for his past sins. Can you tell us if Islam does not ask for a convert to atone for those that they oppressed? Is Tate doing any atonement? Does Islam tell us to not show any caution with new converts whose actions prior to conversion were oppressive and who are known to do things to gather more attention and supporters? When Muawiyah converts, do we let him take on a leadership role because his past sins are forgiven? Or do we ask him to be quiet and work on his soul? History teaches us what happens when such people become leaders.