For someone who breezes around this forum with an air of superiority and assuredness of your own fucking knowledge on everything you're unsurprisingly wrong.
Under the Equality Act 2010, race is a protected characteristic, and you must not therefore be discriminated against because of your race. Race can mean your colour, or your nationality (including your citizenship). It can also mean your ethnic or national origins, which may not be the same as your current nationality.
Doing an accent isn’t discriminating against him because of his nationality anymore than doing a Jose impression or a Dyche impression is discriminating against them because of their nationality.
Did he mock the voice, or did he do an impression of him where he mocked what he was saying?
For someone who breezes around here being wrong about everything..