Well... I just got my two males neutered and now the flame-point Makushin, cannot stand the other cats pressence and just attacks him or runs away. Any ideas, tips, etc... Thank you.
What StefanZ said about the different smell is probably true. I have had the same experience many times. It should stop when they get to smelling "normal" again. Shouldn't take more than a few hours, maybe a day (guessing) though for them to settle back down.
Its the vet's smells and the operation smells. Try sprinkling some cornstarch baby powder on all the cats and brushing it in the coats so they smell the same.
Keep the boys by themselves for a day or two then re-introduce.
A lot of people seem to recommend putting pure vanilla underneath the chins of both cats along with some on the base of the tail so they both smell the same.