Most politicians would find that argument confusing and not agree with you. I don't think the outcomes of running to government would be what you expect. It could easily backfire.

Politics is a spectrum. Some claim that model is oversimplified but it's not. Here you're making a left wing argument that individual bad actors must be regulated for the good of the collective. However, left politicians would look at the situation and see the opposite. They prioritize an authoritarian safety-first victim-first mindset, in which individual freedoms are sacrificed to help the weakest. But companies like Google and Apple are already doing that. And whilst you're trying to hammer this situation into a left wing framing, the number of individuals who care about the freedom to install apps from anonymous developers is very small. Trivial, on the scale of a country. They do not represent the "consumer interest" in any meaningful way.

So if you lobbied politicians this way, Google/Apple would lobby back and they'd say, we are exactly what you always demand! We're acting proactively to protect the victims by limiting the freedoms of bad guys for the greater good. And the left would be not only highly receptive to that message, but having suddenly become aware of what is technically possible would likely demand they go much further! We already see this with left wing governments banning VPNs and DNS resolutions so they can better control the internet in order to keep this or that group safe.

Which sort of politicians care about the rights of freedom-loving minorities over the safety of the collective? Libertarian politicians do. But they are themselves in a minority, and would not be receptive to an argument framed as "we must regulate the big evil corporations for the greater good", because regulation is always about removing freedoms: in this case, the freedom to design a computing device as you see fit. They probably would be receptive to an argument of the form "it is important to be able to distribute code and communicate anonymously", but prioritizing something so few people care about is exactly why they don't tend to win elections.

So there's no direct solution in politics, but the closest approximation is to support politicians who are more libertarian than average. They won't solve the problem but they will at least not make it worse, and might be open to very targeted regulations that can be framed as protecting market competition e.g. requiring unlockable bootloaders can be framed as protecting competition in the operating systems market. Meanwhile you can try and increase the popularity of platforms that prioritize freedom over safety. In practice that means demonstrating some sort of use case that the big vendors disallow, which is valuable, morally positive and requires anonymous app distribution.