Also, what we need to understand is that China is a communist country. The major companies are controlled by the government in one way or another, or at least theoretically could be.
You want to boycott the UK or US government, just boycott their government. Don't need to boycott all the companies.
Barack Obama went to Steve Jobs and suggested that he build iphones in the US, and got laughed out of there.
Here's how some US companies reacted to US immigration ban on muslim countries, according to the atlantic: "Tim Cook wrote to Apple employees, criticizing Trump’s immigration order in uncompromising terms, as did Facebook’s Mark Zuckerberg. Microsoft and Amazon have since announced plans to challenge the order in court."
Elon Musk,who has publically said he does not support Trump, withdrew from a presidential council later on - meaning he essentially now refuses to even talk to him - all the while making electric cars that totally contradict Trump's love on fossil fuels and pulling out of Paris accord.
Buying a product from a company in a Western company in a capitalist country doesn't mean you are supporting the government. I don't see, how for instance, boycotting a Tesla as a protest against US bombings in the middle east makes any sense.
Can we imagine if Xi Jinping asked the CEO of Huawei to join some kind of leaders council and the CEO publically refused, citing opposition to Xi Jinping's policy of mass incarceration of muslims? (Assuming it's even possible for him to get such a statement on state TV or the internet without it being deleted.) A few days later there would be a new CEO of Huawei.
For all we know, Xi Jinping is on the phone right now to the CEO of Huawei suggesting to him that a production location be moved. None of us would ever know. And that "suggestion" will not be likely be refused.
Totally different situation.
To a large extent, if you buy a Chinese product you are supporting the Chinese communist party which nowadays is kind of in a way the world's biggest corporation. It's not a very clear situation but all the books and articles I've read on the topic broadly support this viewpoint.
And that's a key reason why Xi Jinping is likely the most powerful person on the planet right now by a clear margin. https://www.forbes.com/powerful-people/list/
The other is China's lage population, and therefore its government has power over more people.
If you buy an iphone, you are just supporting Apple, not the US government.