Parents of S.T.R.I.K.E, I cannot speak on the ethics of Imgflip. It's not the website itself that could be bad, it's the users that make up this website that determine what goes on. This man here contributes to the positive aspect. I see him interact in a positive, wholesome, encouraging manner with others. I believe taking this aspect of him from him would do more harm than good. If him having an account took you by surprise, I can understand how that may be unsettling, however, I can personally say that he has been a good example, and treated others with the utmost respect.
Imgflip has personally been a shining light through some of my tough moments. It has allowed me to converse with others who have gone through similar things as I have, and assist me with problems nobody else can. The users on here are mainly positive, and very friendly. If you're worried about images being shown to your child, ones you wouldn't expose him to normally, I can personally assure you that those images are banned, and removed from the website nearly as soon as they are posted.
Thank you for your time,
A non-creepy random internet dude