Legal and privacy issues aside, if someone has contacted you via unsolicited email, they are almost certainly violating a code of standards for conducting academic research.
I am not an expert in this subject, but the ethics of using public data sources to obtain email addresses seems reasonably well established in academia. I cannot attest to the standards of any particular institution, but from what I have read, researchers are generally required to show that participants in the email sample were not recruited via unsolicited email invitations. And if the participants came from an email list, they would have to verify that the individuals contacted had a "reasonable expectation" that they would receive email contact for research specifically.
I hope this goes without saying, but Stack Exchange was not a party to this survey, so no such relationship would seem to exist.
It's nice to see that they are disclosing fully who is the sponsor of this survey so that participants may(so you can make an informed judgment), but from what I understand, such email invitations should also clearly communicate the name of the sample provider (✓ check), the relationship of the individual to that provider and how that information was obtained, and clearly offer the choice to be removed from future email contact. I did not receive the original invitation, but from what you provided above, much of that information is incomplete.
This is not a legal judgement, — nor do I know how universally the ethics policies I describe above apply, but — but if the University of <Anywhere> feels that the unsolicited collection of email is a valid way to conduct academic survey research, I would be greatly disappointed.