re: Can someone explain to be how sobriety check points are legal?

How else is that supposed to read other than the moment that a cop stops you at a checkpoint that you are determined guilty?
Multiple people are stopped at checkpoints, sometimes hundreds, with a minimal number of arrests.

Because that's what it is. If you go through a checkpoint, you are guilty of driving under the influence. They can search your vehicle with no warrant, sieze your assets, jail you, forcibly remove your blood, and send you before a judge even if you have committed no crime.
Again, the odds are very low unless you are in fact driving under the influence or have drugs, etc in plain sight of the officer through the glass.
The search is conducted after reasonable suspicion has been established or incidental to arrest.
Items (cash) can be seized but is not forfeited until determined by a judge.
You can be jailed when arrested. Many simple DWI can be released with a summons dependent on you BAC being low.
Yes they can forcibly take your blood after a judge signs a search warrant.
Remember to read the statement when you sign to get your drivers license, cuz you agreed to submit to testing as a condition of getting your license. Driving is a privilege not a right.
You go before the judge to set bail after being accused / arrested for a crime. A judge or jury determines innocence or guilt, not the cop on scene.

If you go through a DUI checkpoint and the police decide that they are going to test you, you are automatically guilty. That is a fact.
That is NOT a fact as most people pass thru checkpoints and continue on their way.

That is reality, not your generalized broad brushed statements with no merit. But you do you. You can continue to say it, but you ain’t right in your facts.