"or that dreamer": and not one who is under some misapprehension.
"he is to be put to death, for he has spoken perversely of the L-rd your G-d": Now does this not follow a fortiori, viz.: If one falsifies his neighbor's words, he is (in certain instances) to be put to death, then if (as a false prophet) he falsifies the words of the L-rd, how much more so!
"who took you out of the land of Egypt": Even if your only indebtedness to Him were His taking you out of the land of Egypt, would that not be sufficient!