A comment like "got any sources for that?" without adding additional context is low effort and inching towards trolling.
Another difference is while the parent post of that person's comment it would be nice to include sources, it is about a general topic people can attempt to look for public sources themselves. Your comment you are accusing a forum user (dang) of something and there is no reasonable way to look for sources backing up your opinion/claim.
>>Spectr+(OP)
no, asking for sources is legitimate, it's a crazy world you live in where being asked to give a source for information is low value and/or low effort.