If you argue the terms of the contract, you give them the contract.
For example, if you were speeding and they stop you and say you were doing 80 miles per hour in a 50 miles per hour zone and you say I was ONLY doing 55 you gave them the contract. You admitted that you are in a contract and now the debate is over the terms of the contract.
A proper response could be, "I neither admit nor deny anything and the burden is on the prosecutor to prove every element of his case. The biggest element that he has to prove is whether I was carrying passengers or property for hire to make me liable for his speed signs."
A simple way to look at it is if somebody comes up to you on the street and says where is my $50. If you give him the $50 then you must have owed it to him. Or if you say that I paid you $35 last week, you admitted the contract. The proper response could be "since when do I owe you anything?"
Yet the IRS sends out letters demanding money every day and people just pay it over, or respond by saying; "your codes say that I paid all that is required", thereby admitting the contract.