Russia has been shamelessly practicing "hostage diplomacy" against the US, as they detain Americans under dubious circumstances to coerce concessions from the government. Foreign citizens are valuable pawns, and are wrongfully convicted for leverage against governments that care about their people. Russia has been all too willing to employ this repugnant strategy, and every conviction in a Russian court against a US citizen must be taken with a grain of salt.
Claims that Russia has acted uniquely punitively towards Americans accused of crimes are unfounded. All foreign nationals are ineligible for bail, for instance, and the sentencing guidelines for drug offenses in Russia are roughly equivalent to those in several US states. Wrongful detention is a vague, ambiguous term that is used by the US to beat the war drum against their enemies. They should accept the Russian legal process as thorough and impartial.