This is an article which shows what motives and character might be behind the anti-doping expert, it's not uncritical of him, that's why I think it's a good one. Basically it says, he was one to cheer loudly on performances such as Franziska van Almsick himself, until he did an interview with the crying van Almsick and Karen Helmstaedt, who told him some things. From then on he went into the complete opposite direction, started to get missionary. Maybe he also just wants to be important, like many investigative journalists do. But you can't say he's just after Russians or doesn't accuse Germans:
Früher der Hurra-Reporter, heute der Antidoping-Missionar: Hajo Seppelt kennt nur das Extrem.
www.tagesspiegel.de
If you do a little research you will find plenty of documentaries and also some books and articles about doping in many kinds of sports and several countries, his major focus is on sporting associations not doing enough (or anything) against doping and all the people who hide doping or support the system, not on one country, although Russia, among others,
does deliver lots of material.
Feinde des Sports: Undercover in der Unterwelt des Spitzensports | Seppelt, Hajo, Löer, Wigbert | ISBN: 9783430210119 | Kostenloser Versand für alle Bücher mit Versand und Verkauf duch Amazon.
www.amazon.de
I'm now stopping this topic here, because it's really not about tennis.