All these arguments about how India is going to take over Sri Lanka and integrate is to the union is all but PDF Indian fantasies, Real world is vastly different..
As for the reason of the opposition from Lankans are manifold
1. The political climate is not conducive, Especially politics of attrition towards the sovereignty and territorial integrity of Sri Lanka from Tamil Nadu which this may connect with goes on unabated, With the Central govt of India having little control..
2. The territorial borders of the island are violated daily by TN poachers in their thousands stealing and destroying marine wealth of the country, Most these trawlers owned by political class in TN.. again te Central govnt of India or thier coast guard doing little to prevent this
3. Hundreds of Indians are working illegally in the country having arrived on tourist visa's, For a small country even a few hundred is a huge problem, Having a history of indentured labor bought over by colonists in their thousands and changing demographics in the country artificially that led to a series of issues on instability, People are quite jittery of such prospects,
Remember SL is a island nation, So it's inhabitants have a certain degree of island mentality.. They see 20 million people fighting for their unique identity against 80 million just across the straight
I'd agree this fear may be unfounded but with such a volatile history you cant blame the general citizenry
3. As
@Godman rightly pointed out road infrastructure from ThalaiMannar to the mainland is not sufficient to this project also it's not in the interest of the GOSL to invest on infra in that area because of the sparse population
4. As for CEPA, Thats not going to happen either, The govt has renegotiated another agreement, Which restricts the service sector for Indians due to the opposition from Sri Lankan professional bodies
PM insists no CEPA, new deal with India, China | Colombo Gazette
Also note somebody mentioned about thousands of Lankans working in India.. Well thats not entirely true, A lot of Lankan students study Medicine and Engineering in Indian Uni's but almost all dont seek employment there most prefer go back to SL other move on to Western countries, Most of others are Tamil refugees in Southern India, Also Indians working illegally in Sri Lanka are exclusively laborers and illegal traders of small goods.. So the two circumstances are entirely different