The leader of Sinn Féin publicly demonstrates her party’s beliefs:

Sinn Féin criticised for ‘England get out of Ireland’ banner

… and the unionists are all butthurt:

Bigotry and hypocrisy still alive and well within the Sinn Fein version of republicanism - Swann

I understand why the Unionist may be upset, but the DUP clearly just wants to get the spotlight off of how Brexit is going to mess up NI.

Explanation demanded from Sinn Fein leader Mary Lou McDonald over ‘England get out of Ireland’ banner

The DUP (whose social stands are more similar to creationists here in the US) are going to have an increasingly hard time as Brexit makes it clear that NI will have a hard boundary with the RoI, given what the atavists in UK politics (the Brexiteers) are intending.