Nope, just make SMS an optional field, along side with your email marketing. SMS is all about the ROI, with a 97% open rate, it's hard NOT to do it.

If you're a spammer, yes you'll destroy a relationship. If you're an ethical marketer and find the correct opportunities to use SMS, you'll see some great results.

Not sure I understand "quit trying to destroy your customer relationships with sms marketing?" What do you mean by that?