So my question is now is the crime of plagiarism more offensive than scamming? 
Both are important to get the forum's attention. not only in this forum but more institutions and other communities also prohibit plagiarism. then the forum will make special rules for accounts that commit plagiarism.whereas scammers and forums are not moderated. but they are a concern for other users. tags in the account will be a consideration for anyone not to deal with scammers. although the account is still active on the forum, it still has a warning attached to its account, limiting the work it can do.
It is only in this forum that plagiarism has a heavier punishment that scam. And I understand that the reason it is like that is because there actually a way to detect whoever that plagerised and then punish him/her.
But there is no easy way to determine that someone is a scammer. So, deciding to moderate scam may end up victimising the innocent.