If the websites states something to like:
By clicking Like, you agree that you have read and accepted........

Is that not a contract?
Assuming that the person doing the clicking is able to enter a contract.
e.g. not a child or cat

and this folks is why you do not use your real name on social media sites.

"Click like and you cannot sue" sounds like a sweeping generalization.
More likely ... you may not sue for anything gone wrong on the web site at which you made the agreement.
Still ... exactly what could you get (or not get) from their web site that you'd ever sue for?
I think this is a canard.

But if you get sick from eating their cereal ... that stands outside of any agreement made on (or off) their web site, and you could sue.

General Mills: Legal Terms

The part in red is probably what all the fuss is about...

ANY DISPUTE OR CLAIM MADE BY YOU AGAINST GENERAL MILLS ARISING OUT OF OR RELATING TO THIS AGREEMENT OR YOUR PURCHASE OR USE OF ANY GENERAL MILLS SERVICE OR PRODUCT (INCLUDING GENERAL MILLS PRODUCTS PURCHASED AT ONLINE OR PHYSICAL STORES FOR PERSONAL OR HOUSEHOLD USE) REGARDLESS OF WHETHER SUCH DISPUTE OR CLAIM IS BASED IN CONTRACT, TORT, STATUTE, FRAUD, MISREPRESENTATION, OR ANY OTHER LEGAL THEORY (TOGETHER, A “DISPUTE”) WILL BE RESOLVED BY INFORMAL NEGOTIATIONS OR THROUGH BINDING ARBITRATION, AS DESCRIBED BELOW.

Informal negotiations
To expedite resolution and control the cost of a Dispute, you and General Mills agree to first attempt to resolve a Dispute informally for at least thirty (30) days before initiating any arbitration. Such informal negotiations will commence upon written notice from one party to the other. You must send your notice to *Removed*. Please include in the subject line of the email “Request to Negotiate.”

Arbitration procedures
If you and General Mills are unable to resolve a Dispute through informal negotiations, either you or General Mills may elect to have a Dispute resolved by binding arbitration by notifying the other party of such election. Either party also may choose to seek relief in a small claims court for a Dispute within the scope of its jurisdiction, instead of arbitration. To make this election, the small claims court action must be commenced before either party notifies the other of an election to arbitrate the Dispute, but after the conclusion of the informal negotiation period described above. If neither party has validly commenced a small claims court action for a Dispute, any election to arbitrate the Dispute by one party will immediately become final and binding on the other.

You and General Mills agree to waive the right to litigate any Dispute in court (except in small claims court in the limited circumstances described above) and before a jury and agree that this arbitration provision will be governed by the Federal Arbitration Act to the maximum extent permitted by law. You and General Mills also agree that any arbitrator that arbitrates a Dispute under this provision is without jurisdiction to conduct a class arbitration or other representative proceeding, and may not consolidate one person’s claims with another.

You and General Mills agree that all issues of enforceability of this agreement to arbitrate – including issues relating to scope, validity, and unconscionability – will be decided by the arbitrator. If for any reason this arbitration provision is deemed inapplicable or invalid, you and General Mills both waive, to the fullest extent allowed by law, the right to a jury trial and any claims relating to a Dispute to recover punitive or exemplary damages and any right to pursue any claims on a class or consolidated basis or in a representative capacity. These waivers shall also apply to any proceeding in small claims court.