I am personally all for gay people to get married and adopt kids, and yes homophones do piss me off. But I believe in freedom of speech no matter how wrong or obnoxious we may view certain opinion´s of people. It should not be a criminal offence to voice your own opinion.
Firstly know that I am not homophobic (if anything, I'm homophilic), however one must take many factors into account when considering this question to address it fairly.
What is meant by "should".. Are we talking about opinions or absolutes here?
What are the standards for legislation?
What is the purpose of legislation? (Or what "should" it be? What should be considered a criminal offense?)
I see no legitimate reason to make homophobia a criminal offense, especially not in any country that supports freedom of speech or belief. It really depends on what the goal of legislation is determined to be. However I don't think any common goal for legislation would necessitate such a thing. I personally don't like the idea of putting anyone in prison for holding a particular belief or doing something anything that is not of direct consequence to others. While I would support criminalizing homophobic acts involving violence, I would support criminalizing them not because they are homophobic, but because they are violent.
Homophobia literally means - the dislike of or prejudice against homosexual people.
To DISLIKE someone or have a PREJUDICE against someone isn't enough to become a CRIME. If you are being violent or verbally abusive, for example, because of that DISLIKE and PREJUDICE, then that is wrong, and should be appropriately dealt with.
Otherwise, it is simply ridiculous.
Example: One may subconsciously be prejudiced against big men, because the may look aggressive, or dislike pretty girls because they make you feel ugly. So what? That isn't a crime.
So technically, being homophobic shouldn't abhorred (nor should it become a crime). Not to the extent it is these days. It is about what you do with that dislike and prejudice that really matters.