If a partner is oppositional, you must respect that. You can't force Poly
on anyone and if you do so in any way (either by convincing, mollifying,
compromising) and they comply or bend, it's not had a 'good start'. That,
in fact, will be a poor start and lend itself to problems that will
eventually show up in splintered stressed relations or even resentment.
Basically if you don't get your foundation in place effectively, you're
building on shaky ground and will eventually fall apart -- not a symptom of
Poly, per se, but a symptom of bad relationship building. If a partner is
oppositional to this, then the best way to gain trust and respect is to back
off and wait. That wait may mean you never get what you want -- but you've
not damaged the other person's trust of you, the other person's ability to
accept Poly in the future or even you. Whether the other person agrees or
enters into a poly relationship, you must treat them with respect and care,
regardless.
Just a few thoughts.
M