I had giardia as an infant, and I'm fine

This whole giardia discourse is driving me crazy because of how violently misinformed and obtuse it is

2 quick premises:

1. Giardia is anything but rare, especially when dealing with rescued animals. In my experience, something like 1/3 of rescued animals has it (maybe people don't know because they buy animals or because it's treated before putting rescues up for adoptions).
2. It's absurd that people have to defend themselves from accusations that are altogether made up and poorly so.

My main point is (and it seems absurd to even have to say it) you don't need to phisically eat feces like straight out of the can to get it. I myself had it when I was extremely young (I think under 1y old if I remember correctly) and my parents are anything but dirty, and they have always taken very good care of me. But what's more WE NEVER HAD ANY PETS! We used to live in an apartment, and at that age I doubt I was roaming around in the park eating poop all by myself. And yet...
Anyway, I did get quite sick, but it was easily spotted and treated.
What's funny to me is that now I do have pets (two cats), and one of them had giardia (a LOT of it) and gave it to the other, but neither me nor my partner got it (and antibodies have nothing to do with it bc it's a parasite). So it can really be unpredictable.

I don't understand how to some people it can seem more likely that someone else has been sippin dierrhea than there is something they are not getting about how giardia works. Is it just ignorance? Is it intentional? Is it a complete loss of critical thinking?