"(whether or not you agree with the decision in the Schenck case.)"

The problem is that the statement was used not only to support the decision in that case, but could be used to support any restriction on free speech rights -- which you yourself have done. You can always claim that allowing some particular form of speech would create a panic or disrupt public order, which it is joking about airport security, handing out anti-draft literature, or voicing disapproval of the president.