
Unfortunately this is not an uncommon effect of castrating a male, especially a young and socially low one, that is submissive. The ones with plenty of confidence have the confidence to put the would be romeos off, the others will be pestered.
A very nice submissive Springer used to come to our training class. He had been castrated as a matter of course at a young age by the ladies vet, and she went along with it thinking it was for the best.
He was terrrified of the other dogs at first, but gradually in the controlled class environement he made freinds and became more confident, so that he3 was less picked upon, but he had to be kept on a lead on walks, as he would run in fear if a dog was persistent.