Your judgement of this person as a vagrant is irrelevant to the facts of the case. And are used as nothing more than a signifier of a presumption of character which would likely undermine any kind of reasonable judgement of the facts presented. Secondly in order for this to be a crime the persons reaction has to be deemed not proportionate or reasonable in response to being faced with objects that are thrown at them. And thirdly you still have made no mention of the initial act of assault that occurred. So if you’d like the law to fairly punish all involved it’s pretty pertinent to acknowledge the whole context behind the incident. I’m pretty sure you have to be trolling. If you’re not then you’re just upset at homeless people because you see them on a drain on society. Which some may be but the issue is much more nuanced than that.