@Mischa Maxwell , this means nothing to you, and I hope it means something to them. Whether the selling of sex is illegal depends on the country where you sell it.
However, a big part of your marketing is to protect your brand. Likewise, we need to make businrss continuation plans for when our suppliers are no more. If mischamaxwell.com is gone forever because squarespace gets in trouble with the American law, then you are screwed, and in this regard, that's not a good thing.
MAKE SURE YOU OWN MISCHAMAXWELL.COM AND THAT YOU CAN SWITCH MISCHAMAXWELL.COM AWAY FROM SQUARESPACE WITHOUT THEIR HELP AT ANY TIME.
Do you have an userid and password to the domain registration? Can you access and edit the mischamaxwell.com registration on Tucows?
If not, you are screwed when Squarespace is in trouble.
If yes, you can happily ignore the matter. If needed, you can host your site elsewhere, with no disruption of business.