No it isn't an oxymoron. At least, as long as you mean bonds as synonym for relationships rather than a synonym for bondmaids
Some bonds really never can be broken - especially when it's emotional bonds. These bonds are invisible, but they are stronger than the strongest steel chain. And the bonds in a real D/s relationship (like between a Master/Mistress and their slave) are even stronger, absolutely unbreakable. For example, I have (or, more exactly, my main account has) worn the collar of the same Mistress since 2008
, and we have grown real close even despite crises that would have made any normal relationships (even in RL) fall apart.
Bondmaids, on the other hand - well, a woman has to be broken to become a bondmaid (or slave in general)