Concerning the lack of service issue: you could file a Motion to Quash and make a special appearance, but you may want to consult with a landlord/tenant attorney in your area to assist you with the preparation of the motion and/or to see if you can negotiate paying rent in order to avoid the time and expense of litigation.
Regarding the Demurrer, that is a complex issue and more facts are necessary in order for a lawyer to provide you with advice. There are various grounds for a Demurrer to be filed (i.e. Uncertainty, Failure to State a Cause of Action, etc.) but nobody on Avvo can tell you what to "say" in the pleading. If there are facts regarding retaliation that can be asserted in the Answer, proven at time of trial, or alleged in a separate Complaint (as no Cross-Complaints are allowed in Unlawful Detainer actions).
The information provided herein (i.e. answers and/or recommendations to questions posted on this forum) is for general purposes only. The posting of this information by G. Michael Brelje, Esq. and the viewing of any posted information is not meant to create an attorney-client relationship and should not be construed as legal advice. If the viewer desires specific legal advice then the viewer is advised to consult with a lawyer in the appropriate jurisdiction and share the specific facts, supporting documents and evidence unique to viewer’s situation.
I am not sure what your sexual orientation has to do with it. Apparently, your landlord believes you have not paid rent and is now trying to evict you. If you did not pay rent when it was due, your being gay will probably not be a good defense.
Contact a local landlord tenant attorney for help.