To nudge this closer to a legal context (but IANAL), I think the GP comment is invoking the general idea of equal protection under the law (http://en.wikipedia.org/wiki/Equal_Protection_Clause). That is, the government should not selectively prosecute cases against those it does not like (http://en.wikipedia.org/wiki/Selective_prosecution).

As the wiki article notes, this kind of argument tends to not be very successful.

One guidepost on when Equal Protection claims are more likely to be successful is the notion of "strict scrutiny" (http://en.wikipedia.org/wiki/Strict_scrutiny). For instance, if prosecutions are taken against people of one ethnic group, then these prosecutions are subject to a higher degree of judicial scrutiny and are more likely to be overturned.

As the parent comment to this one notes, targeting the most lucrative violator would seem to not be prejudicial in this way.