What matters are the consensus rules. To be Bitcoin, you must use the exact same consensus rules. XT, Classic, and BU do not use the exact some consensus rules. They have different consensus rules for a hard fork when certain bits in the version are set and a certain threshold is reached. Those are not the exact same consensus rules as defined by the reference implementation, thus they are an altcoin. It does not matter that they are compatible with Bitcoin, they are, by definition, not Bitcoin.
Don't forget, every soft fork changes the consensus rules. For instance we could soft fork to make the max block size 500kb. We can soft fork, to make it impossible for un upgraded nodes to validate transactions but have them still think they are valid.
exactly, Core is doing softforks only, but by doing so, they are the ones who make the change.
In a hardfork, you are least allow the nodes to vote.
A hardfork is better for the freedom and decentralization because it allows people to choice which fork to support.
A softfork does not allow that choice.
And yet, Core has made people believe a hard fork is evil and a soft fork is the way to go.
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Bitcoin has never intentionally hardforked for a manner you describe.
If a hardfork is performed in the future, it will need preferably over 95% support.
A hardfork with a lower support threshold is a malicious hardfork.
Hardforks with two surviving chains are not a type of voting mechanism.
What you are describing is called a failure of consensus.
You are basically advocating a divide & conquer mentality, cloaked as democracy.