You could start with something like this. Probably will need a little work so use a copy!
Code:
Sub Obfuscate()
Dim osld As Slide
Dim oshp As Shape
Dim iRow As Integer
Dim iCol As Integer
Dim wrd As Long
Dim otxTemp As TextRange
For Each osld In ActivePresentation.Slides
For Each oshp In osld.Shapes
If oshp.HasTable Then
For iRow = 1 To oshp.Table.Rows.Count
For iCol = 1 To oshp.Table.Columns.Count
If oshp.Table.Cell(iRow, iCol).Shape.HasTextFrame Then
If oshp.Table.Cell(iRow, iCol).Shape.TextFrame.HasText Then
Set otxTemp = oshp.Table.Cell(iRow, iCol).Shape.TextFrame.TextRange
For wrd = 1 To otxTemp.Words.Count
otxTemp.Words(wrd) = String$(Len(Trim(otxTemp.Words(wrd))), "*") & " "
Next wrd
End If
End If
Next iCol
Next iRow
Else
If oshp.HasTextFrame Then
If oshp.TextFrame.HasText Then
Set otxTemp = oshp.TextFrame.TextRange
For wrd = 1 To otxTemp.Words.Count
otxTemp.Words(wrd) = String$(Len(Trim(otxTemp.Words(wrd))), "*") & " "
Next wrd
End If
End If
End If
Next oshp
Next osld
End Sub