That is one of the greatest risks, because while you may agree to give them your biometrics for air travel, you may not agree to do it for another purpose, but it's too late at the point where they already have it.
It effectively means that if I don't want them to potentially give it to LEOs, I have to opt out of any services they are gatekeeping behind it.
That's not a slippery slope argument, it's an argument that there is no way for me to review how the information they collect is actually being used.
I don't think you read the EPIC post, or the part I quoted. You're creating a new, more reasonable argument that is loosely aligned with the second, lesser concern that EPIC had.
It effectively means that if I don't want them to potentially give it to LEOs, I have to opt out of any services they are gatekeeping behind it.
That's not a slippery slope argument, it's an argument that there is no way for me to review how the information they collect is actually being used.