This may help.
I am also familiar with that site.
The sight holds a broader membership.
If you had "attacked" the religion of other members then the admins may have taken the poem in that context.
Judging the appropriateness of a post is often subjective.
If, however, you only posted this poem and no other posts addressing other faiths, then I have no idea why they would have banned you.
But welcome to the BB.
It does have a broader membership, but even that membership is highly favorable to catholicism. So long as one is favorable to it, they are accepted. The moment the wicked 'ism' is attacked, you're out.
I am against all false religion, in every forum. I am not merely anti-catholicism.
I will give a for example. In that forum, I posted this in response to a catholic saying they keep the Ten Commandments, I then shared the Traditional Catechetical Formula which leaves out Idolatry, and then posted the following:
Is this an image of kissing the black stone inside the silver yoni, Idolatry?
The catholic would not respond with a simple yes and avoided the question, knowing that I had a follow up question with an image for him of the pope doing the exact same thing with their own iolds. The mods would not acknowledge this, and like I said are catholic based, even if they are not outwardly in the catholic church. They are theological cowards.
They are even syncretistic. There was a post that claimed that the JEHOVAH Elohiym (LORD God) of the scripture is the same God as that of the Jews (presently) and Muslims. I wrote an entire response. I was partially banned the first time (4 days) saying I am attacking the 'trinity' (which is false in Roman doctrine/def., anyway). I gave definitional details demonstrating the difference. They did not care and I got banned for the 4 days.