Feel free to forward any bit of legitimate evidence.
Three of the five corners named to the All-Pro team in 2015 were drafted in the fifth round or later (Josh Norman, Richard Sherman, Chris Harris).
Three of the four on the 2014 All-Pro team were drafted in the fifth round or later (Sherman, Harris and Brent Grimes).
In 2013, two out of the five on the All-Pro team were not first rounders (Sherman and Alterraun Verner).
In 2012, three of the four were not first rounders (Sherman, Charles Tillman and Tim Jennings).
Look at the lists for the all time single season leaders in interceptions. There are two first round corners in the top 28 on the list - Spec Sanders and Ty Law. The Cowboys most productive secondary ever? Thurman's Thieves? Out of the corners that played in that group, only Ron Fellows was drafted in the 6th round, and Dennis Thurman was drafted in the 10th round. The best corner of that group, Everson Walls? Undrafted.
As far as the Hall of Fame is concerned, a greater percentage of running backs in the Hall were drafted in the first round than first round cornerbacks.
Cornerbacks can be found throughout the draft. As can any position in the NFL. As there are minimum of two, and often three corners on the field at a time, chances are that you are finding your producers outside of the first round. It's pretty self-evident.