Conservatives/people who support mass deportations: what is an unacceptable % of false positives?

[Ferguson97]

In the event of mass deportations of undocumented immigrants by a Republican Administration, it is basically impossible that there won't be at least a few "false positives", or cases of people who are here legally being deported anyway, either because they are mistaken for somebody else, due to a clerical error, or even deliberately by a bad actor.

My question to you is, what is the "unacceptable" percentage of false positives? Meaning what is the cutoff to where you would stop supporting mass deportations if you knew that it meant that this % of innocent Americans would be mistakenly deported.