It does not make sense for someone to lose faith in apple because someone else was able to run a modified imessage app.

For apple to entertain this idea is to create more problems for themselves in the long run.

If you understand this from my perspective, which is that these actions are motivated by a desire for more control. It begins to make more sense. If you can benefit from increased control, then these unreasonable expectations of security against your customers (held by other customers) are a desirable problem to have as opposed to an increasing burden.

Imagine the same being said of a car manufacturer. "We need to install security measures in place to prevent you from modifiying your car because other people may see that modified versions of our cars exist and that tarnishes our brand somehow".

As long there is no reason to allow companies to exert this control over consumers, it just allows the manufacturer to enforce a total monopoly on the post-market.