The ANC's criticism of FNB's "You Can Help Campaign" videos shows intolerance, the Freedom of Expression Institute (FXI) said on Tuesday.
"FNB was only giving voice to a view from some young South Africans and this appears to be a useful contribution to our national debate," FXI executive director Phenyo Butale said in a statement.
"The ruling alliance is free to disagree with and criticise the FNB, but it has done so in a way that is threatening and likely to have a chilling effect on debate and discussion."
The campaign features a number of videos of children in school uniform reading their hopes for the country.
Business Report published quotes from some of the videos.
"The country is being overrun by poverty... while [President] Jacob Zuma is renovating his home," said a youth from KwaZulu-Natal.
A university student from Gauteng said: "The government is only thinking for themselves... I'm from a rural area and the government doesn't see what's happening."
"...Politicians tend to be the most destructive and eruptive [sic] aspect of our country... We need motives and a clear vision... We must not depend on our leaders. Each person must become their own hero," said a high school pupil from KwaZulu-Natal.
A Western Cape student said: "I was born in an epic era... We need to stop relying on government and rely on ourselves."
On Monday, the African National Congress said it was appalled by the campaign. The ANC Youth League called it "treasonous".
First National Bank had since pulled some of the videos, but had not abandoned the campaign.
Butale called on the ANC to be more tolerant and open to criticism.
"The ANC has a strong majority and its authority in government is not threatened by such adverts."
The Christian Democratic Party questioned why the ANC accused young people of treason, but was silent about the looting and protesting in the Zamdela township in Sasolburg.
"Instigators in these activities are openly threatening to make the country ungovernable, yet not once have they been publicly accused of treason," CDP leader Theunis Botha said in a statement.
The Freedom Front Plus also hit out at the ANC for condemning the adverts, but not the protests.
"In the midst of the dramatic events in Sasolburg, the ANC finds time to criticise the FNB advertisement campaign, but does not find the time to condemn without qualification the violence and plundering taking place in Sasolburg," FF Plus leader Pieter Mulder said in a statement.
The Congress of the People Youth Movement said the ANC and its league's objection to the advert was taking the country back to apartheid.
"The ANC, ANCYL and ANCWL have come out blazing like in the days of apartheid, where the apartheid officials would want to squash and destroy anything contrary to the government," spokesperson Bongani Mahlangu said in a statement.
"South Africans need a government that will listen to every voice, critic and its young to build a collective better future."