Alright, I'll bite.
Do you plan to wait until retirement to buy a house? Probably not - so don't put the down payment in a retirement account. Think of those as separate goals, with separate time frames. And because you want to buy a house sooner than a retirement account normally allows, I'd agree with putting money in taxable.
If you're flexible on the timing, you can invest more aggressively. You could have a high percentage of stocks, and then switch to cash when you're within 3-6 months of buying a home. The aggressive part is this: if the stock market corrects 6-12 months before you want to buy, you instead wait for next year - the flexibility. If you're buying a house in a specific year, with no flexibility, then you need cash accounts and CDs to make sure the money is all there.