From a Fall 1968 interview with Denise Levertov at Michigan Quarterly Review:

EGB: What is it that happens to some writers who become so heavily involved in espousing causes that they become merely propagandists? What do you see as the reason for this? 

DL: I think that that can happen when an artist is involved in some kind of political ideology that has a party line which he follows. I don’t think that this happens in the peace movements in this country, where so many poets in the last two or three years have been increasingly writing poems overtly concerned with war, because the peace movement in this country is not an ideology, is not a monolithic organization with a party line, which a person enters and gives up his own conscience and thought and becomes subservient to that ideology. The peace movement in this country is just an agglomeration of individuals. Some people say that this is a weakness, that it would have more power or more efficiency if it were better organized. I think that would be only a very temporary and superficial advantage. I think its great underlying strength is that it is composed of individuals who do whatever they do-do their thing-because their own conscience leads them to it, and the proliferation of organizations within the peace movement is a reflection of that fact. I think it’s basically a strength. And I think that artists who get involved with it are not affected in that way that you described, for that very reason. 

EGB: The key might be-when issues touch the individual, then he can react authentically as an artist, but when those issues are on some… 

DL: -theoretical 

EGB:… level, and don’t really concern him as an individual, then he becomes simply a propagandist. 

DL: Yes, I absolutely agree. I think there is no abrupt separation between so-called political poetry and so-called private poetry in an artist, who is in both cases writing out of his own inner life.