Bird-eating spiders are opportunistic. If they happen across a nest, yes, they will eat the young. However, they also eat anything else that comes across their path, and eat birds only rarely. That guy's spider probably died young from such a fatty diet.

Even idiots tend to only have semi-docile snakes free-roaming. Boa Constrictors are not an aggressive species unless they are teased, tormented and starved, and they NEVER get big enough to eat a person.