I know of some believers that will not eat mushrooms because they say they are "fungus" and that they do not qualify as the seed bearing plant. I was doing a mini-study on yeast for my own edification and found this:
are a growth form of eukaryotic micro organisms classified in the kingdom Fungi, with about 1,500 species described; they dominate fungal diversity in the oceans
The yeast species Saccharomyces cerevisiae has been used in baking and fermenting alcoholic beverages for thousands of years.
Now, while I don't subscribe to mans classification per se; however, they do fit together because of similar parameters in behavior.
So - if yeast is a fungus and therefore acceptable, then why wouldn't mushrooms be?