I'm curious what site you are on that they'd cuss you out...seems a little harsh.
At any rate, there's a few you can try...
For poly people in particular....although I think the user base is still pretty small...
POF ... best part, free...largish user base. However, not overly friendly to poly or alternative lifestyles...gender & preference options are very straight forward. There's nothing preventing Bi's or Poly's, but you're only 'supposed' to have one account, and it doesn't let you look for both men & women at the same time on the same account....even if you tell the system you're bi. There's a lot of filters which people turn on to block married people, or casual sex seekers.
OKC is also free...a little more flexible about bi's, and has options for open relationship, although it rephrases things, like open marriage becomes 'Available'. Big thing on OKC is quiz questions to allow the system to match you up with like minded folk. I'm not sure if there's actually a lot of Poly's on there, but you'll probably find a lot of them perkilating in your high %age matches since they'll answer many of the questions similarly.