Way I see it, its any fighters prerogative to say what they want when asked questions like this... whether the answer is true or not. Who cares. We all saw the fight. We can draw our own conclusions/opinions as to who was toughest.
To me, this is no different to GSP saying Fitch was his toughest fight, even though everybody knows the first Penn fight was. Just like Sonnen, Penn talked 2 tons of shite about GSP beforehand. Damn right hes not going to give him kudos.
We all know Sonnen was Silvas toughest fight. I dont care how cool Silvas "god" is, or how much faith hes got. Right before that submission, he thought he was going to lose. So did his corner. So did all his fans. We can talk about whether he means physical or mental toughness. Whatever. Its mentally tough when you've been punched in the face more times than the rest of your career and are 2 minutes away from losing your belt and status. Thats tough. Not going into a championship fight with Franklin only to realize within the first minute that this guy is easy prey for you.
Let Silva say what he wants. He deserves it. After all, as a fighter, he is beautiful when in full flow. He can say anything and I will still love him. By the same token, we can say whatever the feck we want about them. What a tangled web we weave...