One could argue that it's at least a bit of cherry-picking.
Furthermore I would not agree with the statement that those incidents is a major contributor to the stigmatization of the political left - the socialist. That I would think is caused by massive propaganda and scare mongering throughout the 20th century.
They also forgot to mention that at that time, the government branding them terrorists were killing them and their compatriots at many of the labour sit ins.
Usually it's the elite that's quick to justify thousands of death for security, so I'd argue that while deplorable in a moral sense, the acts themselves when taken in context are understandable, as it was war.
