Right - now define "reasonable".
And keep in mind that Title VII is applicable only if it does not impose an undue hardship on the employer. Now define "undue hardship".
My guess is that Allstate will argue, in response to the lawsuit, that the article in question will or could cause them to lose business among a targeted demographic (gays) and/or that it created a hostile work environment for their gay & lesbian employees. Those, among other defenses they will surely use.
Finally, guess who usually wins these things - the employer or the employee?
Homosexuals are not protected by Title VII. The history of Title VII and, quite possibly, its text, in include the point that a customer's objections to dealing with a person of a particular employee's race or religion is NOT a legitimate basis for an employer refusing to hire, promote, or retain an individual. The concept of "reasonable accommodation" is a generally intrusive one that applies to what an employer has to do with employees' on the job religious demands, such as a Jew requesting Saturdays off. In this case the employer needed to do no more than leave the employee alone on the employee's own time.
The employee did not advocate any illegal actions against homosexuals; he only expressed and defended his scripturally correct religious beliefs about homosexuality. What he did is no different than saying the Ten Commandments require children to honor their mothers and fathers and write an article saying how children should do so.