Don't pay attention to what they claim, they claim many things. Even if 10% of their claims were true, they would be a major economy and a major power in the world after 72 years of independence.
I honestly have no problem with Jamat or any other Islamic party doing Islamic politics in BD. BD is the third largest Muslim country in the world by population, it's only natural that there would be Islamic politics. I only have problems with their connection with Pakistan, for this reason alone they should be banned forever.