Is it abuse for daycare workers to argue in front of children?

No: I would not consider an argument that daycare workers have amongst each other abuse. Inappropriate, yes. Adults should refrain from arguing in front of children. It is inappropriate for daycare professionals to be doing this. It may be scaring the children who are witnessing this, and teaching them inappropriate behaviors.

Depends on situation: If the arguments are typical spiteful rants with little value other than blowing steam, i find them worrisome. If, however, they are productive episodes in mutual respect , enumeration of issues, finding common ground & reaching a mutual resolution, they can teach a kid how disagreements should be resolved.