So you’re basically saying that someone who grew up secular doesn’t know religiosity, and therefore the argument "I was once on your side" is valid?

According to this argument, it would be enough to find one Jew who converted to some other religion, and then every Jew would have to get to know Buddhism / Hinduism / Shinto / Christianity / Islam / and the rest of the package….

Of course, one can reject a priori religions that led to backwardness and cruelty, but that same consideration would reject Judaism too.
It’s enough to look at the Haredi politicians who represent "Torah wisdom" model 2024 and understand that "Torah wisdom" is a mixture of stupidity, wickedness, greed, and selfishness, and then there’s no need to investigate the technique behind "Torah wisdom."

Adi, if I write it again, will you stop asking whether it’s true? I wrote it, didn’t I?

Gabriel, it’s a good thing there’s no censorship on this site for demagoguery and obsession, and not even for drawing incorrect conclusions. Your short message here has all of that goodness.

Okay…
In my opinion this argument is correct, but not always. Also, you’re assuming that the other side doesn’t know your side (unless they explicitly told you so). But as a collective and systematic argument for bringing people back to religion, it’s simply not correct. There are secular people who know the other side, or were even religious in the past, so in their case this argument is worthless.
After all, what is this whole argument basically saying?
"I know something you don’t."
Which is fine, but it’s not a good argument for bringing someone back to religion…
The reality for most people is that we don’t know the background of the "other side," just like all the religions and cultures Gabriel listed. By that same logic, a Buddhist could come to me claiming that I don’t know his religion, and he’d be right, but that’s not an argument that would draw me to his religion.
What would move me is if he presented me with facts on the ground.
It’s amazing how simple this is; I don’t understand why people make it so complicated.

To Adi,
You wrote in the question whether a person who used to be secular and returned to religion has an advantage over a person who was always secular, so yes, he has an advantage. That doesn’t mean he is necessarily right.

What kind of advantage, and in what sense? If the intention is that he specifically knows about his own world and about one very specific religion that he entered, then fine—but that’s an advantage that has nothing to do with bringing people back to religion, because it doesn’t enter into the equation of whether it’s true or not. It’s like if I told you: this person has a higher IQ than a secular person—so what? There are lots of advantages; the question is which of them count as a function we should take into account when we want to persuade someone of our position. At most, you could say that because he was on the other side, he may be able to understand the secular person better than a religious person would (although even there you’ll find suitable conversation partners who understand everything; a person doesn’t have to have been secular necessarily… as the Rabbi said, there are religious people who know secularity).