I happened to closely follow the alarming emergence of HT in Bangladesh over the last 5 years -- alarming because they openly reject democracy as "un-Islamic", unlike the other Islamist parties that at least accept the democratic system as a pragmatic norm and act within it. Ironically, when they first started their activities at universities in Dhaka in the name of "intellectual debate", I heard some of these British-accented returned-to-Bangladesh leaders claiming that HT is a "non-violent, non-political" movement (exact words). Imagine my reaction when, less than 2 years later, I come across explicitly political leaflets being distributed outside mosques in Dhanmondi.
It's not entirely true that HT is "totally peaceful". Rather, they have taken on different colors in different countries. In places in Central Asia, HT-inspired movements have been known to engage in openly militant activities. Also important to note, though HT is currently based in the UK, they were originally founded in Palestine over 50 years ago by a cleric named Nabhani. A professor I knew at college, who once personally interviewed the late founder of Hamas, said he happened to meet an HT man in Palestine whose views were the most "extremist" he had ever seen -- even more extreme than Hamas!
Finally the Bangladesh government made the right decision in banning Hizbut Tahrir in Bangladesh.
"The organisation's activities have been banned from today [Thursday] as its activities go against public security."
Hizbut-Tahrir (the Party of Liberation) has already been banned in Saudi Arabia, Jordan, Syria, Lebanon, Egypt, Pakistan, Tunisia, Libya, Turkey, and in the former Soviet states in Central Asia.