Why aren't customer tags showing up after import?

[Mattinnovations]

Hello,

So recently I noticed a lot of our customers listed are spam, fake accounts (names are like xkdodekmodmdd xodnwdn). I tried to fix this by exporting the customers, tagging the fake customers with the tag "spam" and then importing the list again overwriting current customers. For some reason this never works and the tag doesn't show up? I even tried importing a list with only the fake customers and tagged them direct from import. STILl doesn't show any tag.. I need to delete so many in bulk (thousands) and I think it's only possible to do via segmenting through tags... Can't send out marketing emails because of so many bouncebacks from the spam accounts... Any idea what to do here? Why won't tags show up?

Thanks,

Matthew Ortalano