Purely grammatically, it's possible, but semantically, it's odd in the example sentence. で can connect two clauses when they have a relation (e.g. "temporal order" or "cause and result"), but しんせつ and しずかなひとがすき doesn't have such relations.
しんせつで can be considered the -te form of a na-adjective 親切だ. See せがたかくて and あたまがよくて in another example. These are also the -te form of i-adjectives. (the etymology of this で and the -te form of the copula are the same, though.)