You know that Benito Juárez was good friends with Lincoln and considered the Republican his idol. Benito Juárez was anti-Catholic to the extreme and removed all church powers in Mexico and confiscated Roman Catholic Church properties.
Found this interesting document. It suggest that Jefferson Davis, by January 1865, believed institution of slavery was dead and considered joining in an alliance with the Union to fight Maximilian. This armistance was offered by Lincoln.
http://memory.loc.gov/cgi-bin/query/r?ammem/mal:@field(DOCID+@lit(d3997500))
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David Upton