The foreign governments already know, more or less, which dissidents are being supported by whom. It doesn't take WikiLeaks to tell Kim Jong Il where his enemies are getting their M4s or whatever. Secrecy mostly gives governments the room to make deals with groups which the population finds objectionable: genocidaires, nazis, theocrats, thugs, etc. For example, Nixon secretly made deals with the Vietnamese communists to sabotage peace negotiations; Reagan was secretly dealing with the Iranian theocracy and with the Nicaraguan contras (who had a bad rep stateside due to rape, murder, and so on). It is in fact routine for the US government to make deals with violent extremists or autocratic governments, very often in direct opposition to democratic movements or governments.

Diplomacy is a very complex game, but you seem to be confused about which side the players are on. Politicians are on one side, you and I are on the other.