Meaning of “Gaizin(害人)”

“Gaizin(害人)” means harmful foreigner. This has the same pronunciation as “Gaizin(外人)” which means foreigner.
This is an slang on internet.

As you know, the number of foreign tourists in Japan has been increasing recently due to the weak yen.
We welcome those who love and enjoy Japanese culture! Please come and have fun in Japan!
However, it is unfortunate that the actions of a few individuals—such as troublesome YouTubers who use abusive language, very disrespectful tourists who deface shrines, and illegal immigrants committing crimes—have become more noticeable in Japan recently. As a result, this slang has been appearing more frequently on the internet.

Example Conversation

A: There are more foreigners in the city lately, huh?
B: Yeah, it’s because of the weak yen. As long as they enjoy themselves while respecting the rules, it’s fine.
A: Right. The problem is just “Gaizin(害人)”!!

A: 最近街中に外国人増えたよね
B: 円安だしねー。まぁマナー守って楽しんでくれるならいいけどね。
A: な。問題は”Gaizin(害人)” だよ!!