One of those is a business decision about what to do with their private property the other is an external actor demanding what you do with your private property.
The company control their private property.
The labour can only control their own labour, so they choose to use that control.
How is that not in their right?
I totally agree, they all have the right to not work there, but they don't really have a right to prevent others from delivering packages to a building.
Yes, but people still have the right to say "Pay us $X and ensure safe working conditions or we strike" Tesla can either withdraw or negotiate. Nobody's right is infringed here, it's just free market. Especially as usually the workers have it worse than companies.
> the other is an external actor demanding what you do with your private property.
And why is that bad? You've just described a negotiation between two private parties. In any negotiation, parties try to get their counterparty to do something with their property.
Workers are negotiating with the company about the sale of private property that they possess (aka "labor services"). Of course, workers can also organize together, it's simply an exercise in free speech.