But this topic intrigues me, so I want to keep discussing it if you don't mind.
I don't mind, although it's not a topic I'm super deep in the research on. I can give you basic outlines of answers, but there is a growing lit base on the topic, including some popular press coverage and some lawmaking back and forth that I would encourage you to look at if further interested. I have read research over the past few years that I will refer you towards in terms of search possibilities or things you may not be considering, but as this is a rez discussion rather than a direct debate, I likely will stop there.
The issue I still have is this: If an employer currently doesn't even look at people who check the "I've committed a crime" box, then what will change if you get rid of the box? Nothing, because the employer obviously doesn't want any people with prior convictions to work for him, and he'll find their crime records even without a box. Same goes for colleges.
This makes several assumptions. 1) That extensive work outside of a review of a candidate's resume/possible cover letter is done prior to an interview, 2) that all employers are private companies, while municipal jobs are actually a very common and large pool of possibilities, 3) most people think of all convictions as equally bad regardless of type or time, 4) that employers see any conviction, for any reason, as making someone unfit for any legal work. Even if we prove the latter is true more often than not, there's also many reasons to think that's a very bad societal standard that should be pushed against, and making it harder/more expensive to do so is therefore an advantage.
There are studies on this so you can see what actually changes when the box is removed. Municipal jobs, in particular, show substantial increases in hiring people who were formerly incarcerated without a box on the application. As noted above, it often encourages employers to meet their potential employees and get to know their personality and skills so they can then judge a conviction in that context. Remember that stigmas are often about ideas or groups rather than specific people, and so adding the context of a specific person can certainly break a stereotype.
Further, design choices have real, tangible effects on behavior. There is a huge body of research on this. Including the box forefronts the importance of someone's record in a way we may not even be entirely consciously aware of. You may also be interested in studies of how equally qualified candidates with "white" or "black" sounding names are treated in hiring processes. This actually becomes important in box discussions, because some research indicates banning the box helps people who were formerly incarcerated and white, but hurts black people regardless of their record because more assumption is made of criminality in their cases. There are many ways (un)conscious gatekeeping modes are created and enforced, and they sometimes act unexpectedly.
It seems that what you want is really more of a mindset change than a policy change.
It seems like you do not think these go together, especially in a world of imaginary fiat. I think you'd have to do some work on making the distinction between mindset change and policy change and explaining why it matters. This is another reason why actor is important this year. It also depends whether an aff is claiming advantages off of mindset shift (gay marriage passes so everyone stops discriminating against gay folks because the government says it's chill now), or things that are clear results of a policy change (gay marriage passes so discrimination is now banned at a governmental level, this results in housing/tax/whatever measurable changes).* Overall, I see this as a debatable distinction and not at all obvious in a world of fiat.
You want people to examine each person and not immediately discount someone just because they have a prior conviction of some sort. This is a laudable goal, but the problem is that the existence of a box doesn't make any real difference to people's mindset.
Calling you out here for making assertions without reading the research on real, measured changes. You need to explain those tangible results away, as discussed a bit above. You may be right in some aspects and wrong on others, right with some employers and wrong with others. Nuance is real here.
I also think you underestimate the institutional power of continuity. An alt hypothetical conversation: "Why is this box on our application?" "Because it always has been." Many, many things in institutions go unquestioned until they are, and then they can either be justified or changed. But not asking/thinking about something because it just is that way is more common and damaging in any institution than you may think.
Topically, there are also distinctions worth thinking about here between public and private universities and their distinct roles/rights in the culture.
*loose example to demonstrate a different advantage claim, not interested in gay rights debate here