my country is India. My parents were part of the "Indian Tamil" community and the people who fight for freedom is "Jaffna Tamil". I will try to answer your questions.
LTTE gets its arms and money from its supporters, raising taxes, etc. LTTE uses force because of indiscriminate killing by the Sri Lankan army and governtment when the tamils used to protest by peaceful means. LTTE cause so much pain because the Sinhala community has so much pain. Only the pain of the Sinhala pain is highlighted in Indian media. The Tamils have suffered much more at the hands of Sinhalease than the other way around. SL Tamils differ from Sinhalease community by language, religion, history and culture. Its the same difference as between lets say Malyalees and Manipuris. This doesn't mean Sinhalease and Tamils cannot live with each other but they can only live with each other if there is understanding that the island belongs to the minorities such as Tamils as well. If SL condemns the LTTE, its like approving all the human rights violations of Sri Lanka against the Tamils. The question to ask is whether the Sinhalease has condemened the SLGovt for the mindless violences against their fellow citizens Tamils. LTTE killed Rajeev Gandhi because Indian troops came to the island to provide peace but continued allowing the SLG to settle Sinhalease in Tamil areas after kicking out Tamils. People lost houses and property like this. This made the Tamils angry but the actual war started when Indian army handed over high ranking LTTE personel to SLG (before any fighting with Indian troops) which was against the spirit of peace and these officials killed themselves than face torture. Rajeev Gandhi was not totally interested in peace, he was only looking out for India interest through the Trincomalee harbour. The Tamils were fighting for their lives. Its very different. LTTE cannot come into mainstream politics because after over 50 years of independence, the SL government has continued to discriminate tamils in property ownership, jobs, etc. The question is why can't the SL government treat tamils as equal minorities and sidestep the LTTE. The Sinhalease government has no interest in giving Tamils equal rights. These questions are not difficult to answer. Giving up is definately not a wise solution. You should read http://www.newsweekly.com.au/articles/2007feb03_s.html
It highlights how Buddism is not your usual peaceful "Dalai Lama" type of Buddism. In 1983, when Tamils were killed, it was the Buddist Bikkhus who generally lead the crowd to kill, burn, etc. Remember, LTTE was a reaction to discrimination not a pro-action. In Sri Lanka, recently a government MINISTER said that thos Sinhalease who promote peace will be dealt EXTRA-JUDICIALLY.
Those who live by the sword .. die by the sword I hope this is true, then the Tamils will be free. I have lived in India for most of my life. My parents were moved to India when Sri Lanka took away the citizenship of many many tamils who had lived there for some generation. What you need to think is whether India would EVER treat its citizens like that. So if SL has given the same treatment to its minorities like India, then we can say LTTE is bad. But if SLG is killing Tamils from the 60s, discriminating from the 40s, then we have to think whether the fight is not justified. If the congress government started killing Gujaratis (for example) just because they are Gujaratis, wouldn't you support the Gujaratis to fight the government back. You should read a lot. I thank you for asking me these questions. None of my friends in Delhi know much about it and appreciate my explanation.