Why not then - in that case - choose to use disagree, dislike, or other emojis to signal your disapproval?
The problem with the laugh emoji (used in such a context) is that there is nothing to distinguish between, or, to signal whether it is - or has been - used to laugh at (as in, jeer at) - or laugh with (share a chuckle) - a poster (or a post).
Thus, unlike act of pressing on (clicking) the "like", "dislike", "anger" etc emojis, to signal a response to a post, there is a clear - and equally, clearly, an ambiguity, - when one clicks on the "laugh" emoji, as one does not quite know whether a post is laughed at, or, laughed with.
My own, personal, suggestion (response?) is that the forum have (create? design?) - at its proverbial finger-tips - two distinct designs, to allow for the expression of these two different, respective, emojis, designs that can clearly allow one to distinguish between a desire to laugh at (sneer at, mock, deride) and a desire to laugh with (share a chuckle with, allow for the expression of a shared outlook on life, the universe, with a reluctant - but shared - grin)....