The credit card transaction can't be double spent after 180 days (or however long the chargeback period lasts).
Bitcoin can't be double spent after your transaction is seen by the majority of mining nodes (ca. 10 seconds). Then, after a few blocks are mined (~30minutes) bitcoin offers unparalleled security.
TL;DR: When comparing credit card transactions' vs bitcoin transactions' hardness, use similar metrics for confirmation.
Chargebacks are not quite the same. There's an investigation and so on. I can't repeatedly take my credit card out, buy $2000 cameras, and claim I didn't. Bitcoin doesn't have that safety measure.
The only other feasible way to double spend a merchant would be to scour the topology and find a client that has low latency to the merchant you are trying to defraud, but much higher latency to any significant hashing power. Unless they have their node configured to accept incoming connections, which is not recommended for merchant nodes, the attack is very difficult to pull off and requires a significant element of luck to work.
There are also companies like BitPay that will absorb the risk of a double spend in addition to handling your payment logistics, for a fee less than the typical credit card fee.
For example, our service[1] clears transactions in seconds.
[1]: https://yumcoin.com
However, the cost of doing so (in processing power) is high enough that it's not worth doing for small amounts. So long as amounts over $100 wait for confirmation you should be fine.
My understanding of Bitcoin implementations is pretty vague, though, so I'd welcome correction if this isn't actually how it works.
Right now, you can walk into a convenience store, buy a pack of gum, pay with your credit card, and the transaction clears within ten seconds or so.
From what I understand, a bitcoin transaction isn't set in stone (that is, the money could be double-spent) until it's placed in a block that someone mines - and to prevent problems with people mining the same block twice, multiple blocks. Since one block is mined every ten minutes, we're talking significant time to process a transaction.
There are ways around this - but IIRC they involve an intermediary that both sides trust. That intermediary is unlikely to work for free, so it looks like there would still be a problem.
It's possible that I'm misunderstanding something, or that someone has come up with a clever solution to this problem since I last checked - in which case, I'd like to know what the answer is.