Clearly an absolute necesssity. Consider the following analogy:
10 friends are going out for dinner. They decide to pick the restaurant democratically. Here's how they vote:
- 4 want restaurant A (and hate B)
- 3 want restaurant B (and hate A)
- 2 want restaurant C (and hate A and B)
- 1 wants restaurant D (and hates A and B)
Under the awful British system of first-past-the-post, the friend group ends up going to restaurant A. The majority of diners hate that restaurant.
Under proportional representation, the largest of the minorities does not get to impose its will. They get together, rule out A and B as most unpopular and probably end up eating at C or D (or even find there's a restaurant E which everyone is more or less happy with). The point being that no one ends up somewhere they hate and everyone gets something they can tolerate.
Politically, it has been argued that proportional representation leads to governmental paralysis as coalitions find it difficult to agree long enough to build a programme for stuff like govering the country.
But why govern the country in a direction that most people don't want, simply because you're the largest minority? Wouldn't it be better to wait until you can find something that the majority of people can get behind, or at least don't have a strong objection to?
And what's wrong with paralysis anyway? Are there problems so desperately urgent that you need to fix them RIGHT NOW? And even if that is the case, why should that be an opportunity for you to make changes that most people don't want? If there's something bad going on, using the opportunity to get up to shady stuff doesn't say good things about you.
At time of crisis, a government of national unity is the best solution anyway, i.e. get as many differing voices as possible in the room and try to hammer out something that works for everyone. And at times not of crisis, what's the hurry to ram through legislation that most people find objectionable?
Consider the current (14 September 2020) British government.
Off they go, full of vim and bluster, ignoring conventions, threatening to break the law, ignoring dissenting voices, because they can. The majority of the population did not vote for them but they are the largest majority and they will go a-hunting wheresoever they please.
Under proportional representation, they would have been forced to find common ground if they wanted to get anything done. Yes, get all the voices in the room and try to bring the country along with them, as a whole.
With all due respect, that's not happening right now. Watch this space to find out how it ends...