You could remove the classes from the offending jar as part of your build.
configurations {
jarCleanup { transitive = false }
}
dependencies {
jarCleanup 'foo:dirty-dependency:1.0'
compile files({ tasks['cleanupJar'] })
}
task cleanupJar(type: Jar) {
archiveBaseName = 'clean-dependency'
from zipTree(configurations.jarCleanup.singleFile)
exclude 'offending/package/**'
}