It's implied. Unwillingness to abide by a request from a company's legal team, especially after acknowledging receipt, can be used against you in court. Court cases about web scraping and other site ToS violations have referenced received stop requests when considering willful violation.

Are you serious? Did you miss the obvious subtext?

>Please respond to this message to acknowledge that you have received it. If you can resolve the matters specified above in the next seven days, that would be excellent. If you anticipate that it will take longer, please let us know. I’ve cc’d our Legal alias so that in the event that I am unable to respond, one of our product counsels will be able to provide any necessary assistance.

tl;dr: respond and desist or they will escalate to the next step. Legal action is heavily implied, and it's outright foolish for you to read that and somehow think there's no threat to sue, whether implicit or not

I guess the person you're replying to's point was to take it to the next step. Let them initiate legal proceedings (and pay lawyers) to do something.

Maybe it's foolish, maybe it's not, but this email cost Slack the salary of the person for the time it took him/her to write it. At least make them also pay for an hour or two of legal fees to have this taken down.

And in the process be potentially banned from the platform. This could cost OP his job, considering he built this utility to make Slack bearable to use in his place of employment.

How exactly would they ban you? It's not like Slack verifies your identity upon signup. A new email would be sufficient.