Sorry, but while I get some people like the terms "primary" and "secondary," can we please not talk about secondaries as if they were some sort of pet? "Me and my secondary".....perhaps using that person's name, or "girlfriend" or "boyfriend"? It seems somehow so much more humanizing....
Isn't that a matter of opinion? I mean I feel it's less humanizing when I'm referred to as my girlfriend's boyfriend in the context of conversation. Titles are titles. You either use the person's name or their relative title. Boyfriend, girlfriend, brother, sister, mother, lover, primary, secondary... All title's, and none of them actually need to be used at all when discussing the person in question... unless to specifically establish context. I could be talking about my friend john, or my brother john. Yet, we use the titles exclusively all the time. I might start a conversation "My brother...", even to people who know him and I could otherwise just use the name John. But we all do it. Koopatroopa's secondary is exactly that; their secondary. Just like your lover is exactly that; your lover. As far as I've read, the only implication being made that a secondary is a lesser thing in this case is from you.
SKT - My advice would be to talk. If I were to guess, your primary was only talking about the fact that they may experience a bit of jealousy or resentment over the fact that between the two of you, he is now the "single" one - he just got dumped - while you still have your other. I'd say this is no different than two single friends, where one get's a girlfriend, while the other WANTs a girlfriend. The circumstance doesn't make them less friends - but it might make the single one annoyed by his buddies relationship just because of him feeling loneliness. It's pretty common.
Obviously it would be unfair in a negotiated poly setup for him to ask your relationship to cease since his did. That isn't your fault. So just talk it out, and maybe talk it out with your secondary as well, and suggest that you make a little bit more time for your primary while he copes with the current situation - since feelings of loneliness and potential jealousy will be greater than they usually are for him.