Actually, the "equal protection" issue doesn't apply, give that heterosexual acts bear no equality to homosexual acts, both morally and so far, socially and often legally.
The issue here is that homosexual acts are being made out to be "mere sexual acts" on the acceptable (and evaluative) basis of heterosexual acts. And that the defenders of this particular issue/case in Kansas rely on the "equal protection" measure to force their insistence (very important issue to homosexual activism) that "homosexuality" is on equal footing, of parallel status, with heterosexuality.
That is the actual issue of this case, not this one guy's time in prison, but the evaluation process of just what is "equal" and what is not.
I am not, myself in agreement with the acceptability of homosexual acts being on the same page with heterosexual acts, but I do believe and understand that that is what has been ruled by SCOTUS when they overturned the TX law against sodomy. And, no one can deny all the anti-discrimination laws everywhere that include sexual oreintation and sexual misorientation. It is apparent from the above that homosexuality is on the same legal playing field as heterosexuality, as much as I deplore and despise this status. And, the next/current push is obviously "Pedophilia Legality and Equality".