In this age questioning and objecting to Islamic principles is the best pastime of the ‘educated’ yet intellectually impaired. They fail to understand Islam’s approach and vent the anger for their ignorance on the whoever they can – the idea or the people who stand for it.
1) Hudood (prescribed punishments) in Islam are indeed very strict and the mess other legal traditions have created after failing to check the crimes and dealing with the convicts supports the idea of having strict punishments. (the case of the rapist and serial killer Clifford Olson is a classical example of what confused legal traditions can lead to.)
2) Islamic law of witnesses is also very strict. This is especially true for cases involving sex offenses (in which case carrying out hudood requires 4 witnesses) as it relates to two sensitive issues simultaneously 1) Life 2) Honor. In fact it won’t be out of place to say that punishment based on witnesses is extremely rare. When the skeptics say that having four witnesses is extremely difficult they make no revelation.
A classical jurist stated:
لم ينقل عن السلف ثبوت الزنا عند الإمام بالشهادة، إذ رؤية أربعة رجال عدول على الوصف المذكور كالميل في المكحلة كما في الكلاب في غاية الندرة
“Establishment of the proof of adultery in legal proceedings based on witnesses is not reported from the predecessors (salaf), because it is extremely rare for four trustworthy men to witness it in the required way of seeing it like 'collyrium stick in its case' as it happens among dogs .”
3) Islam by the virtue of its very nature of being a religion promising salvation in the Hereafter inspires people to confess the offenses committed so that they may be free of blame in the next world. This ensures some practical examples of the execution of the prescribed punishments (hudood) that duly serve the purpose of deterrence against crimes. The cases of Ghamidia and Ma’iz al-Aslami who were stoned to death by the Prophet (SAWS) are perfect examples.
4) In any case 2) does not entail an offender can go unpunished in the absence of 4 witnesses because the whole scheme of ta’zirat(discretionary punishments) is there. Such punishments can be given for any other evidence including lesser number of witnesses, DNA or any other circumstantial evidence that convinces a judge of the accused being a culprit.
If, for example, a person is accused of rape repeatedly and every time crime is proven through DNA and similar proofs alone, the judge -according to what I understand as the strongest opinion- can even give him capital punishment (though it cannot be stoning to death). Or a judge may even go for such strict discretionary punishment as a deterrence when the frequency of the crime gets on the rise.
5) All this collectively make hudood the ultimate defense against social evils. If 2) and 3) are religiously observed no one will be punished unjustly and 4) will have to be invoked only rarely because seeing someone stoned to death or even lashed in public will tame the animal within most people. This is why the Prophet (SAWS) said,
إقامة حد من حدود الله، خير من مطر أربعين ليلة في بلاد الله عز وجل
“Carrying out one of the legal punishments prescribed by Allah is better than forty nights of (blissful) rain in the lands of Allah.”
 al-Baabarti, Abu ‘Abdullah Akmal ad-Deen, al-‘Inayah Sharh al-Hidayah, (Beirut: Dar al-Fekr, n.d.) vol.5, 278
 Muslim bin Hajjaj, as-Sahih, (Riyadh: Maktaba Dar-us-Salam, 2007) Hadith 4432 (23-1695)
 This is the opinion of the jurists of the Hanafi school (at least).
 Ibn Majah, as-Sunan, (Beirut: Dar al-Jeel, 1418 AH) Hadith 2537. Classified asHasan by al-Albani.