It seems to me that this is all about wording.
If my partner's choices, actions, or associations are hurting me or hurting our partnership, I expect to get a chance to voice my opinion and be listened to carefully. If it's so important to me that I feel the need to put my foot down about it and make it clear I just won't be able to handle it if the situation continues, my partner can then respect my wishes or let me walk away. If I'm making a fuss over nothing, of course, I don't expect to be listened to.
How is that different from the sort of "discussion and negotiation will take place and I'll disregard it if it's being used frivolously" version of the veto that some people here are defending?
I guess the difference is that with the veto in place you promise to be the one to acquiese in the end rather than let your partner walk away. But wouldn't that be most people's choice most of the time anyway, unless we're talking about your partner asking you to drop someone with whom you've fallen deeply in love and with whom you've forged a partnership of your own... in which case most people seem to agree that a veto policy should no longer necessarily be in effect (note that in the original article linked above the writer talks of needing to reach consensus before a long-standing relationship can be ended... doesn't sound like a veto to me at that point, it just sounds like a discussion of an important issue)?
Veto is a loaded term because for some people it truly does mean "I will drop any other partner the moment you say so, no matter what your reasons are, no matter how much I love him/her, and that is that." *shudder* I would hate to think of my metamour having veto power over me, and yet in essence he does because I know that if my gf were absolutely forced to choose, she would choose him... I would want her to. So, again, it's a matter of wording.
If you need the wording for your partner to feel comfortable, fair enough. But understand that it is a very loaded word. And for those who are ardently against it, it may help to realize that, with the variability in how folk apply it, it may be in essence not so different from what you would practice in your life, it's just been given a harsh-sounding label.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.