"Laozai" means foreigner in Cantonese, and usually refers to foreigners, especially those who speak Mandarin. This title was more common in Shenzhen in the 1980s, because Cantonese people couldn't pronounce Mandarin correctly, so they changed the pronunciation of "Ge" to "Lao Song", thus becoming the present "Lao Zi".
Therefore, in some contexts, "fishing for children" may be regarded as a playful title for some foreigners, but it is not necessarily malicious. The specific situation needs to be judged according to the context and the relationship between the two parties.