In other words you're trusting proper software implementation and other Bitcoiners to verify for you. Double spend bugs have already happened in the past that passive node runners didn't detect on Bitcoin and can happen again. Only "manual verifiers" are relevant and unique in this regard and have a real argument. If you don't do this you are not much different from any Monero node runner.

The last part is basically: "Yea I'm strong because my friend lifts weights" 

To keep to the analogy, while your one friend can help you lift something heavy once in awhile, that doesn't make *you* strong, and you're still trusting/relying on him to lift heavy things for you (relying on a few other Bitcoiners to verify for you AKA trusting)