This is not true. While some security is established by the amount of time required to get a confirmation, an attacker with a given hashrate will have a much higher probability of double spending a 1-confirmation transaction in a 10 minute block-time chain than a 10-confirmation transaction in a 1 minute block-time chain. Meni Rosenfeld showed this mathematically:
https://bitcoil.co.il/Doublespend.pdf The trade-off as far as I can see is that with a higher rate of block generation, latency wastes more work, leading to lower difficulty for a >50% attack. For a POW network with a 62.94 TH/s hashrate like bitcoin, a 10% decline in the difficulty of pulling off a >50% attack is probably tolerable, and worth the gain in more quickly secured transactions.
That all does sound inline with my knowledge as well but I think the conclusion in the debate as i remember it ended something like "its more profitable to mine the bitcoin blocks than it is to attempt a 51% attack as most retailers, casinos, and other big businesses won't allow you to run off with something until all 6 confirmations are confirmed which would be about the worth if not more than the hiest and if it isn't then that business is just ignorant and stupid for not waiting for all 6+ confirmations.