Looks like you are right and the recording is illegal in Mass. That law to me is pure garbage in this case. The guy is on a public street and should be able to tape anything he wants whether it is secret or not. Here is the law:
http://www.citmedialaw.org/legal-guide/massachusetts-recording-law
I completely concur. Any audio/video recording in a public place should be able to be done with no restrictions. Laws such as this are mainly used to protect the guilty, who are often police officers and such.