"You just can't" vs. "you can't just "

Solution 1:

As with only, one should exercise care in carefully placing just. In your sentence, you want:

• You can’t bash an ideology just because of what someone has said/done.

Because you want to be perfectly clear that just applies to because.

In the original pair of question, this one:

• You can’t just do that.

Applies just to do, whereas this one:

• You just can’t do that.

Applies just to can’t.

Solution 2:

The two forms are both correct, but imply different things.

just can't

means that not only can you not do it, you really really cannot or that it is not open for debate; just is used here for emphasis: as in "that's just beautiful" or "I just love Picasso". (This tends to be used in less formal speech, especially in recent decades; it is also a common target for ironic use: "You crashed my car? Brilliant. Just brilliant.")

In contrast,

can't just

means that if you only do what you're suggesting, it's something that you cannot do, but raises the possibility of doing something else as well that would then enable you to do it: "you can't just walk up to the King and say hello; you at least have to bow first." "I can't just run a marathon; I need to train first."

Solution 3:

You can't just bash an ideology because of what someone has said or done

means that you can bash an ideology because of what someone has said or done, but you should do more than bashing.

You just can't bash an ideology because of what someone has said or done

means that you cannot bash an ideology because of what someone has said or done, and I cannot believe anybody thinks you can.

You can't bash an ideology just because of what someone has said or done

means that what someone has said or done is insufficient for bashing an ideology, but in combination with something else it might provide sufficient reason.