Did the angels in Gen. 6:2 sin by taking beautiful women?
Angels are created with intellect (wisdom, understanding and knowledge) that is much greater and on a much higher level than humans. Because they have intellect, they are able to question that which is beyond their intellect – which is the hidden ways of G-d. The Midrash relates several episodes in which groups of angels questioned G-d (i.e. He WANTED them to question Him, and He allowed this). In each case G-d revealed the error behind their questions, and showed to them an aspect of His Inner Will that was previously hidden from them. This of course resolved that particular question for all time to follow, so it can never be honestly raised again as a question on the justice or truth of G-d’s ways.
Humans with their meager intellects can come up with the same questions that the angels had. Since the Midrash of the Sages reveals that these questions have already be asked AND RESOLVED for the angels who are on a much higher level than we humans, we should put aside the stumbling blocks of those questions, and move forward to a deeper faith in G-d and a better understanding of His ways.
For example, here is the account of the angels who came to the Earth and took wives from the human daughters (quoted from “The Midrash Says”):
[After G-d (Hashem) created Adam and Hava (Eve), within a few generations their descendents began to engage in wide-spread sin.]
When Hashem was deploring the wickedness of mankind, two angels, Shamchazai and Azael, arose before Him and argued, “Master of the Universe, didn’t we tell you before the creation of man that he would be unworthy and should rather not be created?”
“If not for man, what pupose does the universe serve?” Hashem countered.
“We, the angels, are sufficient reason for its existence,” was their reply.
“I know that if you were to dwell on earth and possess evil impulses as men do, you would be even worse than they are!” said Hashem.
“Just grant us permission to live among mortals and You will witness how we sanctify Your name!” persisted the angels.”
“Descend and do as you suggest,” Hashem told them.
Shamchazai and Azael arrived on earth as human beings. When they beheld the beauty of human women, they could not resist the temptation to sin with them. These unions gave rise to the giants of the generation before the flood who committed the sins of murder, adultery, and robbery.
One obvious lessen we learn from this is not to be judgemental of another person unless you have actually been in his place. Another lesson is that mankind is G-d’s ultimate purpose for creation, and this purpose is so important that it overshadows the fact that many humans will be drawn to sin, and will actually sin G-d forbid, during the period of history before the Messianic Era.