First, if you want to support any group that is against the nation, it is your opinion. As for booth capturing etc., this was most certainly not true for Rajiv Gandhi (About KK etc., I do not know). In fact, he had a huge majority (Maybe due to a sympathy wave but anyway, it is impossible to fake a 4/5th majority by booth capturing). What should I do? Support every mercenary who is obviously killing left and right against my country? You may find excuses/reasons to do so, but not me. Every terrorist obviously would have some kind of sob story and gets some support somewhere.
Of course, your point about politicians is well explained and maybe people being quiet is the problem. However, killing a prime minister is serious (however bad, the country is destabilized) and overlooking that while supporting Prabhakaran who has killed Tamil people too is not for me. Of course, opinions would differ.