if he's doing a research essay he shouldnt choose a very broad subject like the ones you suggested bloody mary. he needs to back up and support everything in his essay which can make it much harder to do if he has to support and research so many different aspects of one general topic. the more focused and narrow his essay is, the better.
a good strategy for a research essay is for it to lay out a problem facing society that some relevant authority is able to solve. basically write the paper to convince them of why they should or should not do x.
I mean, we are talking about a research essay here. Choosing a topic that requires some deep research is probably better than a topic that doesn't require much digging, both for the end result and the experience gained by writing about it. I can understand just wanting to get your feet wet at first though, especially if you haven't written many research papers before.
Also, I believe the topics I mentioned are plenty narrow. All three are direct questions that can be argued for/against. By brown townyzing environmental issues and the cost of rehabilitation / the effects of military action in a variety of contexts / homelessness in America, someone could construct a hard-hitting thesis that isn't overtly broad. On the other hand, I understand their complexity being a concern.