All Protestant Fundamentalists will admit that both Christ and St. Paul encourage celibacy for the Kingdom for those that can accept it (cf. Matthew 19:12, 1 Corinthians 7:32-38). The reason for celibacy for the Kingdom is so that one can devote himself wholly to God. Everyone has the right to choose a life of celibacy. Well, almost everyone.
Some of the Rites of the Catholic Church, most notably the Roman Rite, have wisely chosen to only select men for the presbyterate (priesthood) who have chosen to devote themselves wholly to God through celibacy. All of the Rites of the Catholic Church have chosen to only select celibate presbyters for the episcopate (bishops). Strangely, some Protestant Fundamentalists have chosen to select only men for what they call the presbyterate (elders) who have chosen to marry and cannot devote themselves wholly to God. I say strangely because it doesn't make sense that the leaders of these churches are not allowed devote themselves wholly to God.
These Fundamentalists are quick to say that it is unfair to force celibacy on Roman Catholic priests; however, it is just as unfair to force marriage on their elders.
As with many heresies, mandatory marriage of elders and deacons comes from a misinterpretation of the Bible. 1 Timothy 3:2 says bishops must be "the husband of one wife." Titus 1:6 says priests must be "the husband of one wife." And, 1 Timothy 3:12 says deacons must be "the husband of one wife." A correct interpretation of these verses is not that marriage is mandatory for men that hold these offices, but that if they are married and their wife dies, they are not allowed to remarry. The key word in these verses is one, as in no more than "one wife."
The most obvious argument against mandatory marriage is that there was celibate clergy in the New Testament: St. Paul was celibate. The most common counter-argument is to simply say that Paul was not an elder. If we ask how we know this, we are told, "He couldn't be an elder because he wasn't married."
Not only is this counter-argument based on circular reasoning, it is proven wrong with the original Greek of the New Testament. St. Peter calls himself a presbuteros in 1 Peter 5:1, which is congruent with this counter-argument because St. Peter was married. However, St. Paul calls himself a presbutas in Philemon 9, which is essentially the same word. If one calls Peter an elder, he has to call Paul an elder; therefore one has to admit that there was celibate clergy in the New Testament. (Actually, in these two contexts, the words in question should be translated as senior and not as priest. This is how the Latin Vulgate does it.)