Hi,
I think that's very unprofessional to be asked that at the stage of a potential interview etc. The person who wrote that to you has either made a big slip up in their usual high standard of professionalism or, are very influenced by it all and have a chip on their shoulder if you are of the opposite to what they think.
I'm not surprised for the latter, a person I thought I knew quite well put the phone down on me when we discussed the Brexit as we are on opposing views, I was shocked that he did that as I didn't have him down for being unreasonable, but hey.
It's a massive decision and 'if' there is indeed an exit from the EU, then I think there will be some serious financial, political and social issues as a result. I'm voting 'In'.
Cheers, DtM! West London & Slough UK!