The exchange took place after a debate last week when Representative Frank's partner, Jim Ready, started taking pictures of Mr. Bielat.
According to a Boston Herald video, Bielat asks about the pictures and Mr. Ready responds, "You better get used to it dude."
Ready then says, "It's a free country, isn't it?" and a chuckling Bielat responds, "It sure is, at least if we can get the Congress back."
A spokesman for Frank's campaign said Ready is an amateur photographer who takes pictures at many campaign events and "no harm" was intended.
A Bielat spokeswoman said the "video speaks for itself."