Remove abstracts from .bib?

A good tool for this sort of operation is the program bibtool. To use it for removing particular field you need to create an resource file e.g. remove-abs.rsc containing the line

delete.field = { abstract }

Then invoke this on your original bib file orig.bib as

bibtool -r remove-abs.rsc orig.bib -o new.bib

@Article{test,
  author =   {Author, A.},
  title =    {A title},
  journal =  {J. Jour.},
  year =     2000,
  volume =   3,
  pages =    {6--23},
  abstract =     {Abstract text to be removed}
}

this produces

@Article{     test,
  author    = {Author, A.},
  title     = {A title},
  journal   = {J. Jour.},
  year      = 2000,
  volume    = 3,
  pages     = {6--23}
}