Your printshop isn't a de-facto public town square. Apple, Google, Twitter, and other large companies have inserted themselves into that position.
People like you that just go "government vs private business" miss the entire context, history, and nuance because why that distinction even ever mattered in the past and how it came to be.
In the past, almost every business was closer in practice to being an individual. Your local print shop. Your local hardware store, etc. And for businesses like that, I agree with you 100% , they should get the right to do what they want.
However, private mega-corporations nowadays have more power than most governments at the time the Constitution was signed. When a company has the power to decide what more than half the country can put on their own phone, that's national level power, companies can seriously oppreess people, discriminate, etc, at this scale. Sure, this is a case of stopping a bad person, but there have also been cases of apple censoring apps critical of apple or other awful governmental atrocities in other countries. I'd rather apple not be able to censor anything, than be able to censor things like that.
And your last paragraph is flat out wrong. Freedom of Speech is a concept, that means you are free to say what you want. You might be thinking of the first amendment to the United States Constitution, which is just one thing the US government promises to do.
Do you believe it's actually possible to eliminate malware? I don't, and I don't think fear of that is a good reason to let a megacorp censored and suppress people's rights.
Also that quote wasn't actually said by Voltaire, but I have another out of context and disputed quote for you that's very relevant here:
"Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety."