The High Court has been told that there was "nothing capricious" about the economy minister's plan to publish the names of RHI recipients.
More than 500 businesses receiving the subsidy are opposed to Simon Hamilton's bid to reveal their identities.
They have launched a High Court challenge against the proposal.
Their lawyer had said it was an attempt "to divert" attention from "ministerial and departmental responsibility" for the botched energy scheme.
However, a lawyer for the minister told the hearing that there is no proper evidential basis for him to be accused of acting capriciously.
He said the department engaged in the "proper discharge" of its public function "to ensure accountability".
The barrister said the political consequences of the issue - the collapse of the Stormont Assembly - were "seismic" and that the fallout was "so grave" that a public inquiry has been established.
Flaws in setting the scheme's subsidy rate left it open to abuse, with the overspend estimated to cost taxpayers almost half a billion pounds.
The court heard that 834 firms had replied to a letter from the department seeking permission to publish their details, and that 94% of them objected.
More than 500 firms are members of the Renewable Heat Association, which is taking the High Court action.
'Not a conspiracy theorist'
The hearing had been told that media organisations risked committing contempt of court if they published the names of RHI recipients.
The lawyer representing members of the Renewable Heat Association said it appeared that the energy regulator OFGEM "unlawfully put this information into the public domain".
If this was the case, he added, any third party is bound by a confidentiality clause not to publish.
"I am not a conspiracy theorist, but the Department of the Economy should have done something about this when it is in breach of its data protection protocol," he said.
However, the lawyer representing the department said it was assured by OFGEM last night that it did not release the information.
The judge commented that there was "clearly a risk of damage to anyone who chooses to publish the list".