There are at least three completely separate issues being conflated here: non-violence, political conflict, and imperialism.

There appears to be a whole range of people (including possibly some signatories of the letter defending Sharpe) who appear to think conflict is bad, and even worse than conflict is conflict encouraged by a powerful party such as powerful, possibly imperialist, interests in the United States.

That is an extraordinarily naive and restrictionist view of both democracy and how to engage in political affairs among people. An alternative, more democratic conception is that contests over power are as inevitable a part of human being as love and sex, and that conflict is often a result of such contests.  Furthermore, such conflict can be as good as love and sex if conducted through non-violent means instead of through destructive force. Political domination (an extreme term used to illustrate my argument) by non-violent means (i.e., out-organizing political opponents) is therefore not in remotely the same category of human activity as domination through violent means -- killing people.

The Saul Alinsky school of community organizing puts it this way: There are two ways of organizing people to obtain the results of collective action: through violence, or through managing human relationships. If you're not doing it through relationships, then you are ceding the ground to those who will do it through violence.

Gene Sharpe, and Col. Helvey, and even US-government funded political organizers that have nothing to do with Sharpe, and might even include some CIA agents, are therefore doing good simply by engaging power through strictly non-violent means regardless of their political views regarding neo-liberalism or other "imperialist" frames.

Another way of putting this: Truth and justice are variables that are almost entirely independent of power, but only power can determine the outcome of any social conflict among people.  Therefore, truth and justice can only prevail over falsehood and injustice if justice-minded people are willing to engage seriously, and even ruthlessly with regards to managing human relationships, in political conflict with an intent to prevail over opponents. And engaging in such conflict -- becoming more powerful or even "imperialist" or "dominant" with respect to forces of falsehood and injustice -- is both good and a very useful and rewarding way of spending one's life.