So for me I don't think it's all that far fetched, and imo it makes sense. It's not as though Tobirama said the Uchiha would be stronger if they were all happy loving bunnies.
I mean I suppose as a bloodline limit it's beneficial in some way- instead of becoming broken and losing focus if people you want to protect are in danger/killed, your Sharingan feeds off those feelings and becomes more powerful.
Just my two cents

And yet Sasuke was not strong enough to protect Sakura when she was close to be killed by Gaara, the one who awaken powers to protect her was Naruto.
Sasuke was only mention to cross that line when he almost killed Karin and we know that he was able to awake the reversal Amateratsu when Karin was about to be killed by killer Bee.