Why Congress is so aggressively against Hazare now?

Because he is giving an impetus to the silent majority that oppose their corrupt government ..The congress does not seem to understand that the people who voted them are only a minuscule minority and that those who voted to the opposition outnumber their supporters and that all that they do is not supported by the majority of the people and that to use force to suppress those few who are vociferous in their opposition is an use of force against the majority of the people and that such use of force is suicidal to the ruling coterie who are only a minority .that has come to power due to the defect in the electoral system .In a very populous country the effect of this electoral defect is formidable .