You have proof they'll legalize cocaine and ban cheeseburgers? Whose position sounds the most ridiculous?

Yours: We'll be able smoke crack, but eating donuts will be a no no.

Mine: Fries and crack will both end up legal and taxed by local, state, and national governments desperate for revenue.

The slippery slope is a fallacy unless you can point out the logical step by step progress which will occur. Simply because something is taxed, does not mean it will ever be banned. There's a particularly large disconnect when currently illegal substances are moving towards legalization and suggesting somehow less harmful legal substances will somehow be banned in the same environment.

How about these. Do you have any proof these won't happen?

If we allow the teaching of intelligent design in schools it will inevitably lead to teaching the life of Jesus in history class.

If we ban gay marriage, we'll eventually see amendments against premarital sex, divorce, oral sex, and any position other than the missionary.

If we don't pass a new version of the Brady Bill, people will eventually be walking around with shoulder launched nuclear weapons.

If we ease up on environmental laws, the big corporations will eventually be dumping their waste directly in your backyard.

In general people pull out the slippery slope theory because they can't successfully defend their position on its merits,. Instead they choose a universally undesired outcome and state that failure to adopt their current position inevitably leads there.