If I was a vegetarian, i'de be asking "if not animal fat, then what?". Synthetic glue? Vegetable glue (milk-based for example)? All these have their own damages on the biosphere, indirectly. The mining for loads of synthetic products is associated with deforestation, and vegetable-based products can sometimes be orders of magnitude worse (for example listen up and take yout seats for the upcoming crises palm oil has/is/will cause, the media is getting fired up for that one with test articles showing interest (see: nutella)).
I don't get it, instead of taking arbitary stances, can't we take more informed stances? Maybe animal-based binding agents kills the least animals for all we know...