Of course you can respond too. You can use the Government's online consultation form. Alternatively the Christian Institute has a more concise response form.
For further comment, see the post at Defend Marriage in Scotland: Dirty Tricks from the Scottish Government?
UPDATE: Thomas writes in the combox:
Actually, it appears that submissions from outside of Scotland have been accepted from the beginning of the 14-week consultation. It's just that the Scottish Government managed to assure the Scottish Catholic Parliamentary Office that only submissions from Scotland would count. At the same time, they also managed to let those campaigning for the redefinition of marriage know that external submissions would actually be accepted. It's all about creating the illusion of a groundswell of support.
The adage about an 'unlevel playing field' comes to mind...