I don't consider picketing a funeral to be free speech. I consider it harassment of the people attending the funeral who are not being dicks. The people who organized the funeral have rights to the land for the duration of the ceremony, and they should have the right to decide who can and cannot attend. You have the right to free speech, but you don't have the right to intrude on a private ceremony or place and demand that people put up with you. If I ran a restaurant and some LaRouches came in and started interrupting meals and the general peace to spread their horsecrap, then I should have the right to refuse service to them and to throw them out. They might say it's "free speech," but in reality my restaurant is not a public place, but private. Technically speaking, the right to free speech only says that you cannot be legally punished or restricted by the government. ("Congress shall make no law...")
Non-governmental censorship would fall under other categories that are already illegal, such as intimidation, harassment, blackmail, etc.