Again, you are making some pretty fundamental errors in logic here. First, quoting a man who was President 200 years ago and assuming his opinion would account for the rapid increase in the flow of information and "speech" is a pretty big jump. During the term of his Presidency, people were lucky to see a newspaper once a week (once a month in many areas) and news took weeks to travel from point to point. The vast majority of people would never do any more "speech" than to write a letter to a relative in another part of the country to tell them about the church social and the spring crops.
Your second assumption is that speech isn't conduct. Speech is conduct, it is an act of volition. It is something we do not just by accident, but with intent and the repercussions that come from that intent.
As an example, would you support the rights of someone to print a book called "the Holocaust never happened - So we need to kill all jews now" Would you consider it acceptable for someone to put up a website that explains how to kill children in a manner that still allows you to harvest their organs for transplant? Perhaps a list of your family members names, their addresses, the codes for their security systems, and the best places to put a ladder to be able to shoot directly into their beds?
The miracle of free speech should always be limited by it's harm to others. In Canada, we don't put up with Holocaust deniers, consider the case of Ernst Zundle... you can always donate to the cause of his lack of free speech on his website
http://www.zundelsite.org/zundel_per...is_zundel.html - Should he have the right to free speech, to teach what is clearly a lie, only because he has MUST have that right? Would you approve of him as a history teacher for your family school? After all, he has the right, no?
The so-called slippery slope exists because through the years, the US constitution has been used (and abused) until it has become a series of bizarre absolutes, legally correct only in the most narrow of ways.