[-Axiom-]

There is a theory among some scientists that the sudden release of the gas contained in these hydrates may have been a trigger mechanism for warming periods in the long distant past.

Some scientists fear that rising global temperatures may cause some of the permafrost to start melting releasing large amounts of methane into the atmosphere.
Methane is a powerful greenhouse gas so yes, this is potentially a bad thing.

This is part of the natural cycle of the earth.

Climatology as a science still in its infancy, there is much we do not understand.
Volcanoes spew millions of tons of carbon dioxide into the atmosphere every year, far more than humanity ever has.
The sun has a far greater effect on the climate of the planet than either.
When studying climate change or global warming (which ever you choose to call it) all of these factors must be taken into consideration to construct an accurate model.
We have a long way to go before we can even begin to understand the how's and why's of climate change.

At some point in the future we will be harvesting these methane hydrates as a fuel source and chemical feedstock.
This will result in even more carbon dioxide to be released into the atmosphere.
What the effect will be nobody truly knows.
Anybody that claims they do know either doesn't understand/appreciate the complexity of our climate or very clearly has an agenda.