tama is a good person but the morals concerning her ability are questionable, originally her ability is only supposed to work on wild animals, and there's nothing wrong about that, but the twist about it being effective on human smile users is a very recent development and that's where things starts to become complicated because the human free will is a sacred subject.
we're all aware of her strong desire to help the allies, and the only way she knows can help is by turning enemies into allies (as raizo and usopp described it) through her ability.
she has been guided to it by luffy the one first who told her to use her ability on a human, and luffy is a conqueror, making use of other people is an essential part of a conqueror's nature same as breaking enemies will or bending them to the conqueror's will, besides the beast pirates are scum who lost their humanity so fuck them anyway.
she's a lonely kid who just wants company, her abilities help in that regard, although the effect only lasts for a month.
i don't like how oda used her in the war, children don't belong in the battlefield, but ongashima has been an amusement park so no worries.