I haven't noticed anything racist in this discussion (though admittedly I haven't read every word of it).

Personally I would be, and have been, just as annoyed by white British people repeatedly asking me for money.

Begging is degrading for people on both sides of the transaction and I don't see that encouraging or ignoring it will do much to help the problems of poverty and homelessness. The whole point of Big Issue selling is supposed to be that it is selling, not begging.