I don't believe Baffert would be stupid  enough to use a banned substance in the Derby. He knows he is the most visible person in horse racing: I am no conspiracy theorist by any means, but something is wrong with this picture. That is my opinion.

It would be very stupid to use something on a Derby horse.  But this stuff just keeps happening with Baffert horses so frequently that I don’t know what to believe.

 When I saw that headline I just could not believe it.  I feel so badly for the horse, which up to now has been a cinderella story.  Baffert knows all eyes are on him: he could not be that stupid or arrogant to dope a horse (for lack of a better word) in the most visible race in the country. I hate to say I think maybe somebody got to his horse, or there is some other reasonable explanation: I simply do not believe it, but the attention this is going to get is just awful for Baffert and the industry. It makes me sad.

Here is the article, the Horse has never been treated with Betamethasone and 21 picograms is equivalent to 2.1 gram. 
The most common use for the drug is to treat psoriasis.

I do not think he is guilty.

Horse Racing News | Paulick Report

Baffert: Kentucky Derby Winner Medina Spirit Tests Positive For Betamethasone - Horse Racing News | Paulick Report

Trainer Bob Baffert announced Sunday morning that Medina Spirit, winner of the Grade 1 Kentucky Derby on May 1, has tested positive for betamethasone, a corticosteroid, and faces a possible disqualification from the race - the first medication DQ since Dancer's Image lost his Derby victory in 1968 after a disputed positive test for the [...]

Read more from Horse Racing News | Paulick Report

 I agree- so many people are assuming he is guilty (based on what I am reading on other web sites)

I know he will fight this very hard, as he should.

I don't know what to believe either, but Baffert has been involved in this before.  I see a long legal battle.

Now banned from Churchill

https://www.thoroughbreddailynews.com/churchill-downs-announces-ban-on-baffert-entrants/

Listen to his press conference. I believe him 100%!
 

ESPN.com

Derby champ faces DQ; Baffert banned by track

Kentucky Derby winner Medina Spirit failed a postrace drug test, news that trainer Bob Baffert called "the biggest gut-punch." Churchill Downs has suspended Baffert from entering horses at the track.

Read more from ESPN.com

CDI does pre race testing and the horse passed that one with flying colors! 

There is a mob mentality out there-- it is pretty ugly