Whenever I see this argument, I get the feeling people can't/don't differentiate between aggressive STYLE and disregard for life or even active enjoyment in killing someone.
Yes, she has an aggressive fighting style, most likely due to her growing up and being trained in a warrior society. But her most defining action, arguably what led to her becoming the chosen of the sun, was that she decidedly won a battle to the death so hard...that she could actually decide not to kill her opponent. I think few people understand how utterly dominating you have to be, in order to subdue an opponent who's after your life, without killin him in turn.
And as far as her abilities in-game are concerned, I see exactly that reflected: She's not just someone who takes all the beatings for someone else (that would be Braum), she's a warrior. But NONE of her abilities are designed to kill. Can they kill with enough stats? Certainly, but so can Soraka's Q and somehow I don't see anyone arguing her being a warlord.
Her Q is a shield bash, the function of which is mainly to stun, her W is a shield to protect herself, er E (the only ability that actually involves her sword) is a gap closer and her most devastating ability....is an aoe-cc effect.
Her passive is the only ability that comes even close to being an ability that's appropriate for killing, and guess what: she can't even trigger it herself.
In fact, her entire kit is, as I declared above, to subdue an opponent without actually killing him.
So yes, the message does come across if you know your fighting. It's just that in the general mind "Protector" is always associated with ridiculous passivity.