Glottalic Theory - a weakness?

I need to answer one more thing:

 

Do you believe that, as in the Glottalic Theory, the IE "voiced aspirates" were really just simple voiced plosives?  Then this would mean that Greek voiceless aspirates and Latin voiceless fricatives evolved from simple voiced plosives like [b], [d], and [g].  Why should the Glottalic Theory be taken seriously if this is what it is saying?

 

Andrew