We are going off on a tangent, alebit an interesting one.
But the point is that lawyers are trained to not make these assumptions, or if they make them, to leave them aside and carry out their professional duty. They may think that Johnny Nicksstuff is guilty, but if he asserts his innocence against overwhelming evidence, then the lawyers has to believe that. And there are further nuances - someone may be guilty of
a crime, but not the one which they are accused, for example. Or, it's possible to act on someone's behalf and test the evidence; or, where someone has admitted guilt to some but not all of the charges against them, to defend them in a trial against those charges etc etc.
The Secret Barrister has a nice summary of this issue
Returning to the original topic...
The answer I suspect is that he's going to have some awkward job interviews! But it's up to employers really; some may not care about the crime, or he may express remorse, or they may view that sufficient time has passed for someone's character to have changed. Loads of people with criminal convictions have jobs, some of them having very good jobs. If he's otherwise an attractive candidate for a job, then in the fullness of time someone is likely to offer him a chance.