No, posting a picture of your daughter doing yoga while wearing a T-shirt with a quote from Game of Thrones on social media is not a threat to do harm to anybody. Thank heavens the folks at Bergen Community College in New Jersey have finally settled that little issue.
This case goes back to January, when a college professor did what was just described above. He posted said picture on Google+. A college executive director got an e-mail notification about the picture post. He saw the picture of the girl, with her shirt that read "I will take what is mine with fire & blood," and thought that this was an actual threat. They put Professor Francis Schmidt on leave (without pay!) and ordered him to see a psychiatrist. More details here.
Months later the college has realized the professor wasn't the one who had lost his mind. Today Eugene Volokh over at The Washington Post has a letter from the college admitting as such:
This letter acknowledges that Bergen Community College ("BCC") may have lacked basis to sanction you for your January 12, 2014 Google+ post of your daughter wearing a Game of Thrones t-shirt (the "Incident"). By sanctioning you as it did, BCC may have unintentionally erred and potentially violated your constitutional rights, including under the First Amendment to the U.S. Constitution.
Upon further reflection on this matter and in order to bring this issue to closure, BCC will strike and remove from your employment file any adverse record in connection with this Incident. … Likewise, any penalty or restriction you may have suffered in connection with this Incident, … is hereby rescinded and acknowledged to be null and void. Part and parcel of this acknowledgement, the Incident shall not be considered in any future BCC decisions concerning your employment, including without limitation any decisions relating to promotion, sabbatical, compensation, or any future disciplinary proceeding. In sum, you will be in good standing with BCC as if the Incident never occurred, and BCC's records shall so reflect.