"By that logic"... wow, couldn't disagree more there, and I don't see any logic in your statement. To me there's a difference to saving lives, an acute situation,... and willingly/ignorantly altering them to suit your own purposes.
They may have been Potentials but they could have gone their whole lives without knowing this. So Buffy telling Willow to activate them is a huge violation of their wills and lives. In their little "empowering" - can stand up, will stand up - segment of the episode we see very young girls being activated (say the one playing softball) so it's not just informed young women in Sunnydale who are coming into power (that would have been vastly different) but thousands of girls who gets no say in this and more importantly - will have no idea what's happening to them. Out of all of these thousands maybe one or two would have been called and actually had to experience becoming magnets for the forces of darkness, unalterably changed and undoubtedly headed for an early grave. Now it's all of them.
(Going back to the empowering segment we see a girl standing up to what is presumably an abusive man in her life, she too is very young, what happens when she strikes him back and kills him? Much like Buffy did with Ted, only this time it's not a robot. By activating the potentials powers Buffy is playing God with their lives. She's not saving them.)
Why, just a few episodes earlier Buffy faces the Shadow Men and finds out how the first Slayer was made.
In her predicament they are willing to further "Slayer" her up, i.e. make her more demon, to which Buffy is horrified and promptly says
Buffy Summers: No, you don't understand! You violated that girl, made her kill for you because you're weak, you're pathetic, and you obviously have nothing to show me.
Because she doesn't want to be more demon, she doesn't want to be more Slayer extraordinaire and have her humanity violated. But she's fine doing this to others? She's fine creating other Slayers that can kill for
her... They have the slayer-hood in them true, but as mentioned, the majority of them would probably have gone on to live normal lives. And her little idea took that from them.
And for nothing to boot.
I mean, if they had spent some time researching the amulet from Wolfram and Hart they could have found out what it did. Because without it, even with those extra potentials, Buffy and her whole merry band of misfits would eventually have been overrun by uber-vamps and died. Meaning, the potential
activation was a stall tactic, not a necessary move to win the battle. They were just little less fodder for the cannons than they had been as human girls.