Section 230 was implemented as part of the Communications Decency Act of 1996. It's similar to the gun legislation, It protects the service provider from being sued when their product is used illegally. It also protects them from being sued for any action they take to remove content.
This legislation protects both ISP's and content provider like coalpail.com. The primary intention at the time was to prevent ISP's from being sued for blocking adult content. The bulk of the Communications Decency Act of 1996 has been removed as unconstitutional but section 230 remains.
https://www.law.cornell.edu/uscode/text/47/230
(c)Protection for “Good Samaritan” blocking and screening of offensive material
(1)Treatment of publisher or speaker
No provider or user of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider.
(2)Civil liability
No provider or user of an interactive computer service shall be held liable on account of—
(A)any action voluntarily taken in good faith to restrict access to or availability of material that the provider or user considers to be obscene, lewd, lascivious, filthy, excessively violent, harassing, or otherwise objectionable, whether or not such material is constitutionally protected; or
(B)any action taken to enable or make available to information content providers or others the technical means to restrict access to material described in paragraph (1).[1]
To reiterate this is a foundation block of free speech on the internet, without this law sites like coalpail.com would be impossible to keep online. While I would certainly support amending it so larger mega services like Twitter would be compelled to provide free speech platform what I would not support is it's wholesale removal.