Here is an excerpt from Simon Baker's book 'Ancient Rome' (the famous BBC Documentary)
"His (Hadrian) drive to excel and his inquisitive mind made him, for example, an accomplished, experimenting architect. The building of a temple to Venus would be the very first mark he would make on the city, the first imprint of his reign. He drew up the plans himself. When Apollodorus, the most famous architect of the day, criticized the proportions of the columns on the drafts that, in deference, the emperor had sent to him for approval, the quick-tempered, unforgiving Hadrian promptly had him killed." (Page 296)
I cannot understand why Hadrian like other emperors where so brutal in their decisions, killing important people, in this case Apollodorus. We call this 'civilised' Rome?