Just sent via the contact form at his official site:
Dear Senator Cotton,
Let me as succinct as possible:
You, your megalomania and the similar characteristics of your fellow politicians are a far greater threat to the security of the American people than dead ISIS terrorists, drug traffickers, kidnappers and child pornographers. Combined.
Fortunately, even if Apple ends up caving to your gang's terroristic demands, strong end-to-end encryption will still remain available to anyone who cares to procure it and use it, no matter how many votes you and your Senate co-conspirators take. Why don't you throw yourself on the floor and hold your breath 'til your face turns blue, too? That will be exactly as effective.
Fuck you very much,