You avoid answering because you know that cash theft is a big hassle.
Bitcoin shares some of the properties of cash. This includes its advantages (direct people-to-people transactions, no account can be "frozen", pseudo-anonymity, etc) but also its inconvenients (thefts are hard to recover). And smanek's point is that if cash is good enough despite its weaknesses, then surely Bitcoin is good enough too.
Furthermore, unlike cash, Bitcoin has numerous ways to palliate these inconvenients. Two examples:
0. You cannot "back up" cash (if you put it in a bank, you lose all its aforementioned advantages), but you can back up bitcoins by making copies of a wallet file. Very useful especially when using deterministic wallets.
1. Cash can only be secured in primitive ways (physical security), but Bitcoins can also be secured by using wallet encryption, storing them offline, remembering them (brainwallet!). Soon you will be able to store them on tamper-proof credit-card-sized hardware Bitcoin wallets protected with PINs or similar.
I will be the first one to admit that Bitcoin is not yet easy enough to be used securely by inexperienced users. But these problems are solvable, and are being solved.
There are in fact some very clever ways to make completely offline and non-physical Bitcoin wallets.