I disagree. They did hear a voice. As it says in Deut. 4:10-13 "Especially concerning the day you stood before the Lord your God in Horeb, when the Lord said to me, "Gather the people to Me, and I will let them hear My words, that they may learn to fear Me all the days they live on the earth, and that they may teach their children… and the Lord spoke to you out of the midst of the fire. You heard the sound of the words, but saw no form. You only heard a voice. So he declared to you His covenant which He commanded you to perform, that is, the Ten Commandments; and He wrote them on two tablets of stone.
Deut. 5:22 "These words( the Ten Commandments) the Lord spoke to all your assembly, in the mountain form the midst of the fire, the cloud and the thick darkness, with a loud voice; and He added no more. And He wrote them on two tablets of stone and gave them to me."
Moses was declaring the moral code that is written in the hearts and minds of all mankind.
The problem occurs when we are faced with those who break these laws. Do you allow marauding bands of evil doers roam the countryside, wreaking havoc on people; killing, stealing, kidnapping your children and selling them into slavery etc.etc. Are we to just say,“We love you.” and let evil people continue in their ways until they “see the light”?