Because compelled speech is an insult to free speech just as censored speech is.

How do you feel about the fact that manufacturers need to list the ingredients of the food they sell you?

Not thrilled about it, and I personally would rather see them repealed. I will concede compelled speech impositions have been interpreted more generously when they are commercial. I don't necessarily agree with it, but even if we concede they can happen, I hope that distinction is made for commercial vs non-commercial content. Though I'm not thrilled with it happening for either.

I will never understand free speech absolutists.

Ads should be marked, ingredients and components should be listed.

What possible reason would there be for a viewer/customer to not be allowed to find out such obvious info?