Question re Republicans and minimum-wage.

Why are Republicans against a minimum-wage?
They say that certain jobs don't deserve a minimum-wage. Some jobs are not intended to be held by breadwinners, but by cheap and exploitable people like teenagers.

That begs the question:
If Republicans think, there are two kinds of jobs in an economy, why would they treat those two kinds of jobs equally?
Shouldn't there be separate job-reports for breadwinner-jobs and non-breadwinner-jobs?

When a Republican is talking about jobs and economy, shouldn't he specify whether he's talking about breadwinner-jobs or non-breadwinner-jobs?
After all, the Republicans have the opinion that the two are not comparable and radically different in economic terms!
From a republican point of view, it makes no sense to mix them!