I'm defensive because I have had conflict with people over it. I'm awkward about both situations because of the idea that acknowledging someone that you are interested in others, are actually close with others, real people with names and bodies and so on, is a more tangible situation and even rejection than a generic 'Exclusivity is not right for me'. This is just residual conventional and hurtful ways of thinking about relationships (the myth that if someone is good enough, you won't ever want anyone else by definition) and I think that A and B understand this intellectually like I do but may still have that sense of rejection or discomfort.
I don't want to make either guy look bad. I do fuss too much about explaining everything, though.
You're right about asking. I shouldn't have asked for a rule of thumb as such because everyone's different!
Okay, I will keep referring to them as friends I'm seeing a bit of and find out a level of affection both are happy with because I do want to be able to express that. If I think the actual situation is okay, then acknowledging it should be as well. Ah, confusing feelings of this being right for me but feeling guilty at the same time!