It's true in the informal sense. Normal people, when considering an "infinitely" bad thing happening (being killed, losing their home, etc) with a very low probability will round that probability to zero (
"It won't happen to ME"), multiply the two and resultantly spend zero time worrying about it, planning for it, etc.
For instance, a serial killer could kill me (infinitely bad outcome) but the chance of that happening is so tiny I treat it as zero, and so when I leave my house every day I don't look into the bushes for a psycho murderer waiting there for me, I don't wear body armor, I am unarmed, I don't even think about the chance of being killed by a serial killer. For all practical intents and purposes I treat that possibility as zero.
Important to remember that different people gave different thresholds at which they round to zero. Some people run through dark parking garages and jump into their car because they don't round the risk of a killer under their car slashing their achilles tendons down to zero. Some people carry a gun everywhere they go, because they don't round the risk of encountering a mass shooter to zero. Some people invest their time and money pursuing spaceflight development because they don't round a dino-killing asteroid to zero. A lot of people don't round the chance of wrecking a motorcycle to zero, and therefore don't buy one even though they look like fun.
The lesswrong/rationalist people have a tendency to have very low thresholds at which they'll start to round to zero, at least when the potential harm would be met out to a large portion of humanity. Their unusually low threshold leads them to very unusual conclusions. They take seriously possibilities which most people consider to be essentially zero, giving rise to the perception that rationalists don't think that infinity * 0 = 0.