I suppose that there are certain aspects of Protestantism that are somewhat similar to Enlightenment values. Reason was central to lots of Enlightenment thought, and to a certain extent Protestant denominations can be considered more 'rational' than their Catholic predecessors. Luther's objection to transubstantiation, the selling of indulgences and ultimately the idea of 'sola fide' could be seen as rational revisions of the Christian faith. Furthermore, the Protestant emphasis on 'inward' forms on faith rather than the perceivably unnecessary forms of 'outward' faith adopted by Catholicism could be interpreted to have greatly influenced Enlightenment thought. Many Enlightenment thinkers (most notably Voltaire) were staunchly against religious institutions, as they thought that they kept the lower classes (often referred to as 'the rabble' by Enlightenment thinkers) in a dogmatic state of ignorance. It may be tenuous, but perhaps the Protestant conception of justification by faith alone might have influenced Enlightenment anti-clericalism.

You have it to a certain extent backwards. The violence of Protestantism sucked up the reforming, humanistic values that were developing alongside it; the enlightenment was these muffled, disarrayed elements finally reasserting themselves (although of course not "just" that). Erasmus preceded Luther.

Secular protestantism isn't protestantism it is humanism.