Well. You have a murderer. They murdered someone in Town B. Town B evicted them. The murderer moves to town A. Town A welcomes them with open arms, even though they would evict anyone who murders.
This is the situation that would exist if we allowed off-site scammers into the community. Kind of stupid, don't you think? The 'what people do elsewhere is none of our business' is absolute rubbish; it would NEVER hold up in real life, and I don't know why the geographical location (or electronic location, however you want to draw a juxtaposition) matters when we evaluate their actions.
There are however obvious differences in the analogy, such as the demographic age-group of people who use sythe.org, potential for character reform, and so on. Factoring all that into consideration:
I would have to support this rule: "Add a stature of limitations of 1 year or more since the offense - Include Black-Hat". 1 year is a long time for development in one's adolescent years, and if they demonstrate sufficient character reform, they should be given a chance, as one would in real life. As for the actual rule itself, I'll repeat, the belief that what people do off-site is irrelevant is stupid. We judge people based on their actions, nothing more, nothing less.