I agree with the minimum tax rate. But I think the criterion for taxing profits should not be where the products are sold (for that, we have the sales tax or the VAT). The right criterion is where the value is created, which is usually the country where the most expenses/employees are.
For example, if an Australian mining company digs up iron ore and sells it to China, it would seem unnatural to tax the company's profits in China. Of course, China might impose tariffs or a sales tax, but the profits should be taxed in Australia.
A strange side effect of this would be that the law of one price on international markets would no longer hold. Imagine you manufactured a product for 10$ that you could either sell for 50$ in a country with a low profit tax of 15% or for 60$ in a country with a profit tax of 40%. Then the rational choice would be to sell it for 50$ in the low-tax country, because after taxes, you still get 44$, whereas in the high-tax country, you would only get 40$ after taxes.
Consequently, a destination-dependent profit tax will lead to lower prices for consumers in low-tax countries and higher prices for consumers in high-tax countries, essentially making the consumers pay for it just like with a sales tax or VAT.
Then the effect would be that all the taxes on facebook, google etc go to the US, not in the countries where they earn the money. The problem exist for example with internet advertising - the local agencies are all doing badly, advertising has moved to the internet - to google and facebook, so they receive most of the money that otherwise would be spent on local radio, print and tv advertisements, the local ad agencies organizing that would pay taxes in our country but now all the money and the taxes leave our countries and we get nothing - no taxes, and no money spent locally. this is what all the countries except the US want to avoid.
The Facebook value is created in the countries they operate through the data they harvest. The work is done by people who use this service.
Any Ad revenue that used targeting in the UK should be taxed in the UK. Simple as that.
Unfortunately HMRC is only strong towards individuals. They wouldn't dare to go after company like Facebook. Even if they did, I am sure, given how little inspectors earn, they'd happily accept an offshore bearer account and quit.
For example, if an Australian mining company digs up iron ore and sells it to China, it would seem unnatural to tax the company's profits in China. Of course, China might impose tariffs or a sales tax, but the profits should be taxed in Australia.
A strange side effect of this would be that the law of one price on international markets would no longer hold. Imagine you manufactured a product for 10$ that you could either sell for 50$ in a country with a low profit tax of 15% or for 60$ in a country with a profit tax of 40%. Then the rational choice would be to sell it for 50$ in the low-tax country, because after taxes, you still get 44$, whereas in the high-tax country, you would only get 40$ after taxes.
Consequently, a destination-dependent profit tax will lead to lower prices for consumers in low-tax countries and higher prices for consumers in high-tax countries, essentially making the consumers pay for it just like with a sales tax or VAT.