Because terrorism is the use of violence by non-state agents to give effect to a political agenda, the essential component of any act of terror is to ensure that the political agenda of the actor is pronounced. It mattes not whether that agenda is getting Americans out of Saudi, getting Israelis out of the West Bank, getting the FBI and IRS out of individuals lives, getting Sinhalese out of Sri Lanka, getting the British out of Ulster, or the Anglophones out of Québec, there is no lack of political agenda to be backed up by violence.
The Red Army Faction (Baader-Meinhof), the FLQ and the Red Brigade were all most assuredly leftist or extreme leftist, terrorist organizations. There is a strong case to be made that the PLO and the IRA were both leftist--at least to the extent that their stronger antagonists were the right wing parties in the United Kingdom and Israel, respectively. We know the politics of all of these organizations. Let us not forget the ANC which was, for many years, a terrorist organization, and demonstrated strong leftist leadings. Their beliefs were paraded out for all to see when they took terrorist actions.
Now, I will grant you that these are terrorist organizations rather than individuals who acted, essentially, alone. But what of Nidal Hasan? After the Fort Hood shootings, his beliefs were trotted out for all to see. (Indeed, to the extent that is has called into question whether he was a terrorist in the first place).
I will certainly agree with you that the editorial position of a publisher will have an impact on how the views of such a person are presented. But I do not think that they affect whether those views will be presented.
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--James