Also, does Nick really believe Aaron is key there? I think Nick holds Aaron responsible for a large part of his current situation. Nick still maintains all that mandatory report stuff wasn't real. Kids clean and fed. The house wasn't a shit hole, it was just cluttered with laundry. Aaron has divulged all the details of his debauchery and made him a laughing stock. Not that he wasn't already. I doubt Nick can really believe Aaron caused him to be arrested.
So I think Nick is more blaming Aaron for his current PR situation than actually genuinely thinking Aaron is important to the case. Seething, basically, and expressing it how he can. Like a 12 year old boy.