DaveO's summary of the main reason Ba'hais are seen as heretical matches my own understanding. (This also leaves Joseph Smith out in the cold, too, to say nothing of Valentine Michael Smith).

This issue does not involve Jews, as the Ba'hai are an offshoot of Islam itself and their relation to mainstream Islam is, as DaveO has mentioned, they regard a prophet of the 19th century as a continuation of the stream of legitimate prophets.

I 'member not long after the coming of the A$$atollah I heard of executions of Ba'hais but I did not hear details.

Maybe I do him an injustice, but if the A$$atollah had a sense of humor it never came out on any of his posters. You'd think the good folks at Scribners would'v'e issued a "Wit and Wisdom of..." book instead of all of us playing name-the-day pool on the lifeline of Salman Rush-to-die (who continues to draw breath long after A-hole-tollah has assumed ground temperature, although I 'spect he be in a warm climate at present)