The alternative is dead organisms plus a quite toxic substance in your water.
Chlorine being toxic in drinking water is your personal opinion. Your opinion is not shared by the people who are experts in drinking water treatment in the US. Chlorine kills microorganisms that aren’t filtered out in previous water treatment steps.
Please cite some evidence that chlorine in drinking water is dangerous to humans at concentrations lower than 4mg/L.
Here is the source, as you requested:
https://www.cdc.gov/niosh/idlh/7782505.html
And here the definition of TLV from Wikipedia:
The threshold limit value (TLV) is a level of occupational exposure to a hazardous substance where it is believed that nearly all healthy workers can repeatedly experience at or below this level of exposure without adverse effects.
So much for that, but it is only half the story. Chlorine is a gas and therefore volatile. The measured chlorine in the waterworks says little about the amount that ends up in your body.
What it does though is, that it forms compounds with organic substances (the microorganisms it kills) in the water, which in turn can be toxic or carcinogenic. Instead of regulating the volatile chlorine it makes much more sense to regulate the harmful compounds, which is exactly what many European countries do.
