Well, even in the city, you cannot tell the ethnic membership of a catholic parish by investigating the ethnicity of its priest. My current priest from home (Nai) is a Kikuyu, but before him, 3 years ago, it was a Hutu who could not speak English; only French and Swahili, before then it was a Southern Indian. Membership depends more on area of residence than the priest. The parish will reflect the ethnic picture of the area it's situated. In Nairobi, this means parishes are always ethnically diverse.
With regard to Cardinal, sometime I wonder if he ever moved around alot? I think he was a Bishop/priest around Central most of his life. He seems to conflate the opinions of his former Gema flock with that of Catholics in Kenya. In any case, the Cardinal is Archbishop only of Nairobi Archdiocese. He cannot possibly claim to speak for the flock of other Bishops, hiyo ni uchokozi. Cardinal is my own Bishop since my home parish is in Nairobi and I have a duty to respect him and obey him in matters of faith and morals and church disciplines but this is not one such matter. If the church has a position, it will come from the conference of Bishops which alone has the authority to speak for the church in Kenya. Even that conference can only ask Catholics to take certain positions where they directly involve matters of our faith and morals, not just what they think is the "best" political decision in a certain question.