The crux of this is a shift in context (φρόνησις) where-in entities like marketing companies or video hosting platforms are treated like moral agents which act in the same manner as individuals. We can overcome this dilemma by clarifying that generally, "individuals with the power to direct or control the speech of others run the risk of gross oppression by being more liberal with a right to control or stifle rather than erring on the side of propagating a culture of free expression whether this power is derived from legitimate political ascension or the concentration of capital."

In short-- no. Your right is to positively assert, "Trump sign" not, "excludes all other signs as a comparative right" even though this is a practical consequence of supporting one candidate and not others. "Owning a marketing company" means that you most hold to industrial and businesss ethics in order to do business in a common economic space. Being the CEO of any company that serves the democratic public means that one's ethical obligations must reflect the democratic sentiment of the public. It used to be that, "capitalism" or, "economic liberalism" meant that the dollars and eyeballs would go elsewhere as a basic bottom line for the realization of the ethical sentiment of the nation-state. This becomes less likely under conditions of monopoly and autocracy. The truth is that Section 230 created a nightmare. If internet platforms are now ubiquitous and well-developed aren't the protections realized under S230 now obsolete?

It would be neat if somebody did, "you can put any sign in my yard to promote any political cause unless it is specifically X/Trump/whatever." That would constitute a unique form of exclusionary free speech.